请问：java代码如何判断服务是否启动？谢谢！！-CSDN问答

请问：java代码如何判断服务是否启动？谢谢！！: 急求： java代码如何判断服务是否启动？谢谢！！; 编辑于：2015.07.16 06:33 发布于：2015.07.16 03:02

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: 小叮当0305

声望： 85

3个回答

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http://www.360doc.com/content/12/0711/09/2905268_223518890.shtml

发布于：2015.07.16 04:07

评论 0 |

| 已采纳

: 大河行脚

声望： 1705

一般服务启动都是启动在某IP的某个端口上，通过Socket去连下你们服务启动的IP和端口。看是否能连的通。如果连的通，表示服务已启动，但请注意，服务启动不代表服务一定正常可用。

附上代码。

    /**
     * 
     * 测试连接服务器
     *
     * @param ip 服务器IP
     * @param port 服务器端口
     * @return 连接成功返回<code>true</code>,连接失败返回<code>false</code>.
     */
    public boolean testServerConnect(String ip,int port) {
        boolean result = false;
        Socket connect = new Socket();
        try {
            connect.connect(
                new InetSocketAddress(ip, port), 1000); //连接服务器，每隔1秒重试
            result = connect.isConnected();
            return result;
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                connect.close();
            } catch (IOException e) {
                 e.printStackTrace();
            }
        }
        return result;
    }

发布于：2015.07.16 03:41

评论 0 |

: Brankily

声望： 245

不知道你说的服务是指什么服务呢

发布于：2015.07.16 05:28

评论 0 |

: yuke198907

声望： 320

: 插入链接

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class="org.springframework.jdbc.datasource.DriverManagerDataSource"> <property name="driverClassName" value="com.microsoft.sqlserver.jdbc.SQLServerDriver"></property> <property name="url" value="jdbc:sqlserver://localhost:1433;databaseName=testdb"></property> <property name="username" value="sa"></property> <property name="password" value="123456"></property> </bean> <bean id="sessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean"> <property name="dataSource"> <ref bean="dataSource" /> </property> <property name="hibernateProperties"> <props> <prop key="hibernate.dialect">org.hibernate.dialect.SQLServerDialect</prop> </props> </property> <property name="mappingResources"> <list> <value>com/svse/entity/Student.hbm.xml</value> <value>com/svse/entity/Class.hbm.xml</value> <value>com/svse/entity/Studentinfo.hbm.xml</value> <value>com/svse/entity/Classinfo.hbm.xml</value></list> </property></bean> <bean id="StudentinfoDAO" class="com.svse.dao.StudentinfoDAO"> <property name="sessionFactory"> <ref bean="sessionFactory" /> </property> </bean> <bean id="ClassinfoDAO" class="com.svse.dao.ClassinfoDAO"> <property name="sessionFactory"> <ref bean="sessionFactory" /> </property> </bean>  <bean id="StudnetImpl" class="com.svse.impl.StudentImpl"> <property name="studao"> <ref bean="StudentinfoDAO"/> </property> </bean> <bean id="ClassImpl" class="com.svse.impl.ClassImpl"> <property name="classdao"> <ref bean="ClassinfoDAO"/> </property> </bean>    <bean id="MyTrans" class="org.springframework.orm.hibernate3.HibernateTransactionManager"> <property name="sessionFactory"> <ref bean="sessionFactory"/> </property> </bean>  <tx:advice id="tx1" transaction-manager="MyTrans"> <tx:attributes> <tx:method name="add*" propagation="REQUIRED"/> <tx:method name="del*" propagation="REQUIRED"/> <tx:method name="update*" propagation="REQUIRED"/> <tx:method name="*" read-only="true"/> </tx:attributes> </tx:advice>  <aop:config> <aop:pointcut id="p1" expression="execution(* com.svse.impl.*.*(..))"/> <aop:advisor advice-ref="tx1" pointcut-ref="p1"/> </aop:config> </beans> --------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------- 配置文件信息跟上个练习的项目中无差别，上个项目中也出现过这个文件，但忘了怎么解决的。请老鸟解决下下，谢谢咯 [b]问题补充：[/b] 恩，1楼，把你说的那段代码去掉后不报错。但后面肯定要用到这的，请帮忙解决 [b]问题补充：[/b] java.lang.ClassNotFoundException: org.springframework.scripting.config.LangNamespaceHandler at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1359) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1205) at org.springframework.util.ClassUtils.forName(ClassUtils.java:229) at org.springframework.beans.factory.xml.DefaultNamespaceHandlerResolver.initHandlerMappings(DefaultNamespaceHandlerResolver.java:117) at org.springframework.beans.factory.xml.DefaultNamespaceHandlerResolver.<init>(DefaultNamespaceHandlerResolver.java:96) at org.springframework.beans.factory.xml.DefaultNamespaceHandlerResolver.<init>(DefaultNamespaceHandlerResolver.java:83) at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.createDefaultNamespaceHandlerResolver(XmlBeanDefinitionReader.java:498) at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.createReaderContext(XmlBeanDefinitionReader.java:487) at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.registerBeanDefinitions(XmlBeanDefinitionReader.java:468) at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadBeanDefinitions(XmlBeanDefinitionReader.java:363) at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:313) at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:290) at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:131) at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:147) at org.springframework.web.context.support.XmlWebApplicationContext.loadBeanDefinitions(XmlWebApplicationContext.java:124) at org.springframework.web.context.support.XmlWebApplicationContext.loadBeanDefinitions(XmlWebApplicationContext.java:92) at org.springframework.context.support.AbstractRefreshableApplicationContext.refreshBeanFactory(AbstractRefreshableApplicationContext.java:101) at org.springframework.context.support.AbstractApplicationContext.obtainFreshBeanFactory(AbstractApplicationContext.java:389) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:324) at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:245) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:188) at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:49) at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3764) at org.apache.catalina.core.StandardContext.start(StandardContext.java:4216) at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:760) at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:740) at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:544) at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:920) at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:883) at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:492) at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1138) at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:311) at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:120) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1022) at org.apache.catalina.core.StandardHost.start(StandardHost.java:736) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1014) at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443) at org.apache.catalina.core.StandardService.start(StandardService.java:448) at org.apache.catalina.core.StandardServer.start(StandardServer.java:700) at org.apache.catalina.startup.Catalina.start(Catalina.java:552) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:295) at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:433) (4219 ms) [main] DEBUG: org.springframework.beans.factory.xml.DefaultNamespaceHandlerResolver#initHandlerMappings : Ignoring namespace handler [org.springframework.ejb.config.JeeNamespaceHandler]: handler class not found java.lang.ClassNotFoundException: org.springframework.ejb.config.JeeNamespaceHandler at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1359) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1205) at org.springframework.util.ClassUtils.forName(ClassUtils.java:229) at org.springframework.beans.factory.xml.DefaultNamespaceHandlerResolver.initHandlerMappings(DefaultNamespaceHandlerResolver.java:117) at org.springframework.beans.factory.xml.DefaultNamespaceHandlerResolver.<init>(DefaultNamespaceHandlerResolver.java:96) at org.springframework.beans.factory.xml.DefaultNamespaceHandlerResolver.<init>(DefaultNamespaceHandlerResolver.java:83) at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.createDefaultNamespaceHandlerResolver(XmlBeanDefinitionReader.java:498) at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.createReaderContext(XmlBeanDefinitionReader.java:487) at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.registerBeanDefinitions(XmlBeanDefinitionReader.java:468) at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadBeanDefinitions(XmlBeanDefinitionReader.java:363) at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:313) at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:290) at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:131) at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:147) at org.springframework.web.context.support.XmlWebApplicationContext.loadBeanDefinitions(XmlWebApplicationContext.java:124) at org.springframework.web.context.support.XmlWebApplicationContext.loadBeanDefinitions(XmlWebApplicationContext.java:92) at org.springframework.context.support.AbstractRefreshableApplicationContext.refreshBeanFactory(AbstractRefreshableApplicationContext.java:101) at org.springframework.context.support.AbstractApplicationContext.obtainFreshBeanFactory(AbstractApplicationContext.java:389) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:324) at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:245) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:188) at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:49) at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3764) at org.apache.catalina.core.StandardContext.start(StandardContext.java:4216) at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:760) at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:740) at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:544) at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:920) at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:883) at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:492) at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1138) at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:311) at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:120) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1022) at org.apache.catalina.core.StandardHost.start(StandardHost.java:736) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1014) at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443) at org.apache.catalina.core.StandardService.start(StandardService.java:448) at org.apache.catalina.core.StandardServer.start(StandardServer.java:700) at org.apache.catalina.startup.Catalina.start(Catalina.java:552) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:295) at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:433) [b]问题补充：[/b] 自动代理的bean？我先前练习的好像也是这样陪的 [b]问题补充：[/b] 还有这个 org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory' defined in ServletContext resource [/WEB-INF/applicationContext.xml]: Invocation of init method failed; nested exception is java.io.FileNotFoundException: class path resource [com/svse/entity/Student.hbm.xml] cannot be opened because it does not exist Caused by: java.io.FileNotFoundException: class path resource [com/svse/entity/Student.hbm.xml] cannot be opened because it does not exist at org.springframework.core.io.ClassPathResource.getInputStream(ClassPathResource.java:135) at org.springframework.orm.hibernate3.LocalSessionFactoryBean.buildSessionFactory(LocalSessionFactoryBean.java:656) at org.springframework.orm.hibernate3.AbstractSessionFactoryBean.afterPropertiesSet(AbstractSessionFactoryBean.java:134) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1198) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1167) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:427) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:249) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:155) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:246) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:160) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:285) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:352) at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:245) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:188) at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:49) at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3764) at org.apache.catalina.core.StandardContext.start(StandardContext.java:4216) at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:760) at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:740) at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:544) at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:920) at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:883) at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:492) at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1138) at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:311) at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:120) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1022) at org.apache.catalina.core.StandardHost.start(StandardHost.java:736) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1014) at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443) at org.apache.catalina.core.StandardService.start(StandardService.java:448) at org.apache.catalina.core.StandardServer.start(StandardServer.java:700) at org.apache.catalina.startup.Catalina.start(Catalina.java:552) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:295) at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:433) (5938 ms) [main] ERROR: org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/Test]#listenerStart : Exception sending context initialized event to listener instance of class org.springframework.web.context.ContextLoaderListener org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory' defined in ServletContext resource [/WEB-INF/applicationContext.xml]: Invocation of init method failed; nested exception is java.io.FileNotFoundException: class path resource [com/svse/entity/Student.hbm.xml] cannot be opened because it does not exist Caused by: java.io.FileNotFoundException: class path resource [com/svse/entity/Student.hbm.xml] cannot be opened because it does not exist at org.springframework.core.io.ClassPathResource.getInputStream(ClassPathResource.java:135) at org.springframework.orm.hibernate3.LocalSessionFactoryBean.buildSessionFactory(LocalSessionFactoryBean.java:656) at org.springframework.orm.hibernate3.AbstractSessionFactoryBean.afterPropertiesSet(AbstractSessionFactoryBean.java:134) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1198) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1167) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:427) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:249) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:155) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:246) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:160) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:285) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:352) at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:245) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:188) at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:49) at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3764) at org.apache.catalina.core.StandardContext.start(StandardContext.java:4216) at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:760) at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:740) at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:544) at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:920) at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:883) at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:492) at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1138) at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:311) at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:120) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1022) at org.apache.catalina.core.StandardHost.start(StandardHost.java:736) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1014) at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443) at org.apache.catalina.core.StandardService.start(StandardService.java:448) at org.apache.catalina.core.StandardServer.start(StandardServer.java:700) at org.apache.catalina.startup.Catalina.start(Catalina.java:552) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:295) at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:433) [b]问题补充：[/b] 有这个包，不少 [b]问题补充：[/b] spring包已经截图 [b]问题补充：[/b] 你说说包的名字吧。你刚才说的那个包确实有，要不我直接把项目打包发你给我看看？ [b]问题补充：[/b] 我想问下我的entity 里的配置文件名字是 Studentinfo.hbm.xml 他怎么报 java.io.FileNotFoundException: class path resource [com/svse/entity/Student.hbm.xml] cannot be opened because it does not exist Caused by: java.io.FileNotFoundException: class path resource [com/svse/entity/Student.hbm.xml] cannot be opened because it does not exist 的错误 [b]问题补充：[/b] 问题已解决，就是因为sessionfactory那个bean下有个student。hbm。xml的原因谢谢你lovewhzlq (资深程序员)

Linux下eclipse启动问题: VMware10.0.1安装了RedHat linux 9.0，JDK装的是1.6.0.45（i586），输入java -version 显示正常，说明配置没问题，但是eclipse启动时候就奔溃了，具体奔溃信息如下，麻烦各位大神看看，因为是学习需要，老师布置的作业，要读操作系统代码，第一次用linux，后生谢谢了 A fatal error has been detected by the Runtime Environment: SIGFPE(0x8) at pc=0x40008d7c,pid=4440,tid=1073951360 JRE version:6.0_45-b06 Java VN:Java HotSpot(TM) Client VM (20.45-b01 mixed mode,shape linux-x86) problemmatic frame: C[ld-linux.so.2+0x8d7c] double+0x9c the crash happened outside the java virtual machine in native code see problematic frame for where to report the bug

切换Activity时报错Unable to stop activity: 请教一下大家，哪些原因可能导致下面出现的问题！程序有两个Activity，从MainActivity启动到NoteActivity时报错，主要是说`java.lang.RuntimeException: Unable to stop activity {<包名>/<包名>.MainActivity}: java.lang.NullPointerException`和`Caused by: java.lang.NullPointerException`，日志里没有说我的代码哪行有问题，都是些系统自己的类和方法。两个Activity的声明： ```XML <activity android:name=".activity.MainActivity" android:theme="@style/AppTheme.NoActionBar"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> <activity android:name=".activity.NoteActivity" android:theme="@style/AppTheme.NoActionBar" /> ``` 启动NoteActivity的代码： ```Java FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab_new_note); fab.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { Intent intent = new Intent(MainActivity.this, NoteActivity.class); intent.putExtra("Open_Type", "newNote"); startActivity(intent); } }); ``` 点了fab按钮后直接报错，完整的错误日志如下： ``` E/AndroidRuntime: FATAL EXCEPTION: main Process: zqy.bysj.todo, PID: 2034 java.lang.RuntimeException: Unable to stop activity {zqy.bysj.todo/zqy.bysj.todo.activity.MainActivity}: java.lang.NullPointerException at android.app.ActivityThread.performStopActivityInner(ActivityThread.java:3174) at android.app.ActivityThread.handleStopActivity(ActivityThread.java:3220) at android.app.ActivityThread.access$1100(ActivityThread.java:135) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1223) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:136) at android.app.ActivityThread.main(ActivityThread.java:5001) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:515) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601) at dalvik.system.NativeStart.main(Native Method) Caused by: java.lang.NullPointerException at android.app.Activity.performStop(Activity.java:5388) at android.app.ActivityThread.performStopActivityInner(ActivityThread.java:3171) at android.app.ActivityThread.handleStopActivity(ActivityThread.java:3220) at android.app.ActivityThread.access$1100(ActivityThread.java:135) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1223) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:136) at android.app.ActivityThread.main(ActivityThread.java:5001) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:515) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601) at dalvik.system.NativeStart.main(Native Method) ``` 请教一下大家，哪些原因可能导致这个问题？谢谢！附图，看的清楚点。 ![图片说明](https://img-ask.csdn.net/upload/201703/14/1489458992_581817.png)

javaservice将jar包制作成windows服务，可以安装，但是无法启动: 最近有个需求，就是写个windows服务部署到内网，每天不断的对数据库查询对哪些满足条件的用户发送短信。我使用的是spring+mybatis,使用maven管理jar包。我实现了第一步：将maven项目打成jar包，然后直接使用java -jar xxx.jar测试运行jar包，发现是可以成功运行的。然后我使用了javaservice将jar包制作成windows服务，安装成功。但是不论是在cmd中使用net start ServiceName 还是到服务列表手动启动，都不能启动，百度了好久，也换过代码甚至工具，都是可以安装成功，启动失败，如下图所示。所以在这里向大家求助，希望大神们指点迷津，谢谢。基本信息： maven工程框架 spring+mybatis 入口一个main方法使用线程+while（true）不间断执行 ![图片说明](https://img-ask.csdn.net/upload/201709/08/1504861317_306286.png)

Java Swing可运行的jar双击启动不能保存文件: 各位，最近用NetBeans做一个Java Swing项目，但是于到了这样一个奇怪的问题。我的代码里有一段用FileOutputStream来写文件的代码，如果在命令行上用java -jar方式运行，那么不会有任何问题，文件可以被正常的写入。但是如果双击.jar文件运行的话，程序也不会报错，但是就是找不到那个用FileOutputStream生成的文件……这是什么原因呀？我在程序后面也加上了flush()，也试过了close()，但是还是这个情况，有点不解…… 谢谢大家了:-)

springcloud zookeeper注册中心，在客服端用restTemplate 访问，第一次访问正常，第二次以后都是失败: springcloud zookeeper注册中心，在客服端用restTemplate 访问，第一次访问正常，第二次以后都是失败：配置以及主要代码如下：服务端： ``` 配置： server.port=8082 spring.application.name=service-zookeeper spring.cloud.zookeeper.discovery.register=true spring.cloud.zookeeper.discovery.enabled=true spring.cloud.zookeeper.discovery.root=/spring-cloud-service spring.cloud.zookeeper.connect-string=cdh01.com:2181,cdh02.com:2181,cdh03.com:2181 java: @RequestMapping(value ="/index") @ResponseBody public AjaxView index(@RequestBody String jsoninfo,HttpServletRequest request, HttpServletResponse response){ 。。。 } ``` 客户端： ``` server.port=8081 spring.application.name=getway-zookeeper spring.cloud.zookeeper.discovery.register=false spring.cloud.zookeeper.discovery.enabled=true spring.cloud.zookeeper.discovery.root=/spring-cloud-service spring.cloud.zookeeper.connect-string=cdh01.com:2181,cdh02.com:2181,cdh03.com:2181 spring.cloud.zookeeper.dependencies.service-zookeeper.required=true spring.cloud.zookeeper.dependencies.service-zookeeper.path=/service-zookeeper spring.cloud.zookeeper.dependencies.service-zookeeper.loadBalancerType=ROUND_ROBIN feign.hystrix.enabled=true ``` JAVA代码： ``` @RequestMapping(value ="/api/{service_name}/{interface_name}") @ResponseBody public String getApiSend( @RequestBody String jsoninfo, @PathVariable String service_name, @PathVariable String interface_name) { String get_url ="http://"+service_name+"/"+interface_name; return backService.getApiSend(jsoninfo,get_url); } ``` 都启动成功后，第一次访问正常，第二次访问就报错了，报错提示没有找到服务列表，但是服务列表确实打印出来了。如下： No up servers available from load balancer ，因为这个提示，没有服务，后续就报错空指针了。但是确实有服务查询到。而且DEBUG也打印出来了。 ``` 2019-05-19 14:37:55.547 WARN 164828 --- [nio-8081-exec-9] com.netflix.loadbalancer.RoundRobinRule : No up servers available from load balancer: DynamicServerListLoadBalancer:{NFLoadBalancer:name=service-zookeeper,current list of Servers=[zhucj:8082],Load balancer stats=Zone stats: {unknown=[Zone:unknown; Instance count:1; Active connections count: 0; Circuit breaker tripped count: 0; Active connections per server: 0.0;] },Server stats: [[Server:zhucj:8082; Zone:UNKNOWN; Total Requests:0; Successive connection failure:0; Total blackout seconds:0; Last connection made:Thu Jan 01 08:00:00 CST 1970; First connection made: Thu Jan 01 08:00:00 CST 1970; Active Connections:0; total failure count in last (1000) msecs:0; average resp time:0.0; 90 percentile resp time:0.0; 95 percentile resp time:0.0; min resp time:0.0; max resp time:0.0; stddev resp time:0.0] ]}ServerList:org.springframework.cloud.zookeeper.discovery.ZookeeperServerList@28667be9 [DEBUG][2019/05/1914:37:55549 ][org.springframework.web.servlet.handler.AbstractHandlerExceptionResolver.resolveException(AbstractHandlerExceptionResolver.java:136)] Resolving exception from handler [public java.lang.String com.example.demo.controller.PageController.getApiSend(java.lang.String,java.lang.String,java.lang.String)]: java.lang.NullPointerException [DEBUG][2019/05/1914:37:55552 ][org.springframework.web.servlet.handler.AbstractHandlerExceptionResolver.resolveException(AbstractHandlerExceptionResolver.java:136)] Resolving exception from handler [public java.lang.String com.example.demo.controller.PageController.getApiSend(java.lang.String,java.lang.String,java.lang.String)]: java.lang.NullPointerException [DEBUG][2019/05/1914:37:55555 ][org.springframework.web.servlet.handler.AbstractHandlerExceptionResolver.resolveException(AbstractHandlerExceptionResolver.java:136)] Resolving exception from handler [public java.lang.String com.example.demo.controller.PageController.getApiSend(java.lang.String,java.lang.String,java.lang.String)]: java.lang.NullPointerException [DEBUG][2019/05/1914:37:55558 ][org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:993)] Could not complete request java.lang.NullPointerException at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:192) at com.google.common.cache.LocalCache.get(LocalCache.java:3931) at com.google.common.cache.LocalCache.getOrLoad(LocalCache.java:3936) at com.google.common.cache.LocalCache$LocalLoadingCache.get(LocalCache.java:4806) at com.netflix.loadbalancer.LoadBalancerStats.getServerStats(LoadBalancerStats.java:175) at com.netflix.loadbalancer.LoadBalancerStats.getSingleServerStat(LoadBalancerStats.java:362) at com.netflix.loadbalancer.AvailabilityPredicate.apply(AvailabilityPredicate.java:73) at com.netflix.loadbalancer.AvailabilityPredicate.apply(AvailabilityPredicate.java:35) at com.netflix.loadbalancer.CompositePredicate.apply(CompositePredicate.java:52) at com.netflix.loadbalancer.CompositePredicate.apply(CompositePredicate.java:40) at com.netflix.loadbalancer.AvailabilityFilteringRule.choose(AvailabilityFilteringRule.java:86) at org.springframework.cloud.zookeeper.discovery.dependency.DependenciesBasedLoadBalancer.chooseServer(DependenciesBasedLoadBalancer.java:64) at org.springframework.cloud.zookeeper.discovery.dependency.DependencyRibbonAutoConfiguration$1.chooseServerByServiceIdOrDefault(DependencyRibbonAutoConfiguration.java:72) at org.springframework.cloud.zookeeper.discovery.dependency.DependencyRibbonAutoConfiguration$1.getServer(DependencyRibbonAutoConfiguration.java:65) at org.springframework.cloud.netflix.ribbon.RibbonLoadBalancerClient.choose(RibbonLoadBalancerClient.java:76) at org.springframework.cloud.client.loadbalancer.InterceptorRetryPolicy.canRetry(InterceptorRetryPolicy.java:53) at org.springframework.retry.support.RetryTemplate.canRetry(RetryTemplate.java:375) at org.springframework.retry.support.RetryTemplate.doExecute(RetryTemplate.java:278) at org.springframework.retry.support.RetryTemplate.execute(RetryTemplate.java:180) at org.springframework.cloud.client.loadbalancer.RetryLoadBalancerInterceptor.intercept(RetryLoadBalancerInterceptor.java:67) at org.springframework.http.client.InterceptingClientHttpRequest$InterceptingRequestExecution.execute(InterceptingClientHttpRequest.java:92) at org.springframework.cloud.zookeeper.discovery.dependency.DependencyRestTemplateAutoConfiguration$1.intercept(DependencyRestTemplateAutoConfiguration.java:67) at org.springframework.http.client.InterceptingClientHttpRequest$InterceptingRequestExecution.execute(InterceptingClientHttpRequest.java:92) at org.springframework.http.client.InterceptingClientHttpRequest.executeInternal(InterceptingClientHttpRequest.java:76) at org.springframework.http.client.AbstractBufferingClientHttpRequest.executeInternal(AbstractBufferingClientHttpRequest.java:48) at org.springframework.http.client.AbstractClientHttpRequest.execute(AbstractClientHttpRequest.java:53) at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:723) at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:680) at org.springframework.web.client.RestTemplate.postForEntity(RestTemplate.java:466) at com.example.demo.util.WebUtil.SendPost(WebUtil.java:86) at com.example.demo.service.BackService.getApiSend(BackService.java:18) at com.example.demo.controller.PageController.getApiSend(PageController.java:60) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:209) at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136) at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:877) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:783) at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:974) at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:877) at javax.servlet.http.HttpServlet.service(HttpServlet.java:648) at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:851) at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.filterAndRecordMetrics(WebMvcMetricsFilter.java:158) at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.filterAndRecordMetrics(WebMvcMetricsFilter.java:126) at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:111) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.springframework.boot.actuate.web.trace.servlet.HttpTraceFilter.doFilterInternal(HttpTraceFilter.java:90) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:496) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1468) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:748) [DEBUG][2019/05/1914:37:55574 ][org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:104)] Cleared thread-bound request context: org.apache.catalina.connector.RequestFacade@46dfd3ba 2019-05-19 14:37:55.585 ERROR 164828 --- [nio-8081-exec-9] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause ``` 请帮忙看看，谢谢。

java 关于NIO实现UDP数据传输问题，急谢谢，C币不足请不要介意: 各位大侠好，小弟想问一下问题，搞了一两天没有搞明白的。因为要实现一个UDP传输服务端，于是在网上找了很多资料然后就写了一个。但是写好之后发现有两个很严重的问题，希望各位大哥给点意见或者思路去解决。问题一：启动服务端，同时也启动客户端，客户端传输数据服务器正常接收，但是断开客户端后，再启动客户端，服务器就收不到任何客户端发送的消息，好像是服务器关闭了UDP一样，但是重启服务器后（重新打开UDP）客户端既可以发送信息过来。问题二：多个客户端。第一个客户端连接上后，第二个客户端怎么也链接不上了。即使关闭了第一个客户端也一样。如下是代码： package com.gateway.socket; import java.io.IOException; import java.net.InetSocketAddress; import java.net.SocketAddress; import java.net.UnknownHostException; import java.nio.ByteBuffer; import java.nio.channels.DatagramChannel; import java.nio.channels.SelectionKey; import java.nio.channels.Selector; import java.util.Iterator; import java.util.Set; import org.apache.log4j.Logger; public class UDPEchoServerSelector extends Thread { private static final Logger log = Logger.getLogger(ServerSocket.class); // private InetSocketAddress inetSocketAddress; // socket处理类 private UDPSocketHandler handler = new UDPSocketHandler(); // 注册的接受服务 private SocketReceiver receiver = null; /** * 初始化socket * * @param receiver * @param hostname * @param port * @throws IOException * @throws UnknownHostException */ public UDPEchoServerSelector(SocketReceiver receiver, String hostname, int port) { if (hostname.isEmpty()) { inetSocketAddress = new InetSocketAddress(port); } else { inetSocketAddress = new InetSocketAddress(hostname, port); } this.receiver = receiver; } @Override public void run() { try { Selector selector = Selector.open(); // 创建选择器，可以处理多路通道。 DatagramChannel serverSocketChannel = DatagramChannel.open(); // 打开通道 serverSocketChannel.configureBlocking(false); // 非阻塞 serverSocketChannel.socket().bind(inetSocketAddress); /* * 将通道管理器和该通道绑定，并为该通道注册SelectionKey.OP_READ事件,注册该事件后， * 当该事件到达时，selector.select()会返回，如果该事件没到达selector.select()会一直阻塞。 */ serverSocketChannel.register(selector, SelectionKey.OP_READ, new ClientData()); log.info("Server: socket server started."); /* * 采用轮询的方式监听selector上是否有需要处理的事件，如果有，则进行处理 */ while (true) { // 轮询 // 当注册的事件到达时，方法返回；否则,该方法会一直阻塞 int nKeys = selector.select(); if (nKeys == 0) { continue; } // 得到选择键列表 Set Keys = selector.selectedKeys(); Iterator it = Keys.iterator(); while (it.hasNext()) { SelectionKey key = null; key = (SelectionKey) it.next(); // 键为位掩码 it.remove(); // 客户端请求连接事件 if (key.isValid() && key.isWritable()) { log.info("Server: SelectionKey is acceptable."); handler.handleWrite(key); } if (key.isReadable()) {// 获得了可读的事件 log.info("Server: SelectionKey is readable."); handler.receiveMsg(key, receiver); } } Keys.clear(); } } catch (IOException e) { e.printStackTrace(); } } public static class ClientData { public SocketAddress clientAddress; public ByteBuffer buffer = ByteBuffer.allocate(255); } } package com.gateway.socket; import java.io.IOException; import java.net.InetSocketAddress; import java.nio.ByteBuffer; import java.nio.channels.DatagramChannel; import java.nio.channels.SelectionKey; import org.apache.log4j.Logger; import com.gateway.common.DeviceDataTools; import com.gateway.common.data.HexUtils; import com.gateway.socket.UDPEchoServerSelector.ClientData; /** * * 处理socket类 * * @author Andy * */ public class UDPSocketHandler { private static Logger log = Logger.getLogger(UDPSocketHandler.class); /** * 链接请求 * * @throws IOException */ public void handleWrite(SelectionKey key) { try { DatagramChannel channel = (DatagramChannel) key.channel(); ClientData clntDat = (ClientData) key.attachment(); clntDat.buffer.flip(); // 从起始位置开始发送 int bytesSent; bytesSent = channel.send(clntDat.buffer, clntDat.clientAddress); if (bytesSent != 0) { key.interestOps(SelectionKey.OP_READ); // 关注客户端发送数据 } } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } /** * 读请求 * * @throws IOException */ public void receiveMsg(SelectionKey key, SocketReceiver receiver) { ByteBuffer byteBuffer = ByteBuffer.allocate(1024); byteBuffer.clear(); DatagramChannel socketChannel = (DatagramChannel) key.channel(); //非阻塞 try { socketChannel.configureBlocking(false); } catch (IOException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } System.out.println("channel code:" + socketChannel.hashCode()); try { while (true) { InetSocketAddress client = (InetSocketAddress) socketChannel .receive(byteBuffer); byteBuffer.flip(); // byteBuffer中传过来的是10进制的bytep[] byte[] dst = new byte[byteBuffer.limit()]; byteBuffer.get(dst); // 将10进制的byte[]转化成16进制字符串 String data = HexUtils.converBytesToHex(dst); System.out.println(data); log.info("Server: data1 = " + data); byteBuffer.clear(); receiver.udpreceive(socketChannel, data, client); break; } } catch (java.io.IOException e) { //e.printStackTrace(); //this.closeChannel(key, socketChannel); } catch (Exception e) { //e.printStackTrace(); //this.closeChannel(key, socketChannel); } } /** * * @param socketChannel */ private void closeChannel(SelectionKey key, DatagramChannel socketChannel) { try { while (socketChannel.isOpen()) { key.cancel(); socketChannel.close(); } } catch (IOException e1) { e1.printStackTrace(); } } /** * 根据socketKey从内存中获取channel，通过channel向client端发送消息 * * @param socketKey * 内存在channel对应的key * @param data * 发送的数据 * @return * @throws IOException */ public static boolean send(String socketKey, String data) throws IOException { DatagramChannel socketChannel = SocketChannelMapper .getUDPChannel(socketKey); if (socketChannel == null || !socketChannel.isOpen()) { return false; } InetSocketAddress client = SocketChannelMapper .getUDPInetSocketAddress(socketKey + "address"); boolean f = socketChannel.isConnected(); ByteBuffer byteBuffer = ByteBuffer.wrap(DeviceDataTools.hex2Byte(data)); if (f) { socketChannel.write(byteBuffer); } else { socketChannel.connect(new InetSocketAddress(client.getAddress(), client.getPort())); socketChannel.send(byteBuffer, client); } return true; } /** * 根据socketKey从内存中获取channel，通过channel向client端发送消息 * * @param socketKey * 内存在channel对应的key * @param data * 发送的数据 * @return * @throws IOException */ public static boolean send(DatagramChannel socketChannel, String data, InetSocketAddress client) throws IOException { if (socketChannel == null) { return false; } System.out.println("#########################ADDRESS" + client.getAddress()); System.out.println("#########################PORT" + client.getPort()); boolean f = socketChannel.isConnected(); ByteBuffer byteBuffer = ByteBuffer.wrap(DeviceDataTools.hexStr2ByteArray(data)); if (f) { socketChannel.write(byteBuffer); } else { socketChannel.connect(new InetSocketAddress(client.getAddress(), client.getPort())); socketChannel.send(byteBuffer, client); } return true; } }

slf4j包的问题: [code="java"]java.lang.NoSuchMethodError: org.slf4j.spi.LocationAwareLogger.log(Lorg/slf4j/Marker;Ljava/lang/String;ILjava/lang/String;[Ljava/lang/Object;Ljava/lang/Throwable;)V at org.apache.commons.logging.impl.SLF4JLocationAwareLog.info(SLF4JLocationAwareLog.java:159) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:273) at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:111) at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4797) at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5291) at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:901) at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:877) at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:633) at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:1114) at org.apache.catalina.startup.HostConfig$DeployDirectory.run(HostConfig.java:1673) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303) at java.util.concurrent.FutureTask.run(FutureTask.java:138) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:619)[/code] 新人，公司的项目，从svn中checkout下来部署到tomcat后启动服务就报这个错，我对代码不熟悉，有人遇到过这个问题吗？求解答，谢谢！

困扰了一整天的bug，求帮助，: 我最近在用Maven做一个Javaweb项目，但是今天碰到了一个问题，我复制了报错信息百度搜索，上csdn,stackoverflow,等网站都没有找到解决的方法，我感觉是数据库的问题，但是我尝试过用JDBC来操作数据库，可以正常连接。数据库账号密码我确认过没有错误，我是跟着视频学的，刚刚接触java不久，希望能够得到大神的帮助，感激不尽全部报错信息如下： ``` java.lang.NullPointerException at java.util.Properties$LineReader.readLine(Properties.java:434) at java.util.Properties.load0(Properties.java:353) at java.util.Properties.load(Properties.java:341) at cn.itcast.travel.util.JDBCUtils.<clinit>(JDBCUtils.java:31) at cn.itcast.travel.dao.impl.UserDaoImpl.<init>(UserDaoImpl.java:10) at cn.itcast.travel.service.impl.UserServiceImpl.<init>(UserServiceImpl.java:9) at cn.itcast.travel.web.servlet.RegistUserServlet.doPost(RegistUserServlet.java:35) at javax.servlet.http.HttpServlet.service(HttpServlet.java:647) at javax.servlet.http.HttpServlet.service(HttpServlet.java:728) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:936) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1004) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589) at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748) 六月 21, 2019 10:40:52 下午 org.apache.catalina.core.StandardWrapperValve invoke 严重: Servlet.service() for servlet [cn.itcast.travel.web.servlet.RegistUserServlet] in context with path [/travel] threw exception java.lang.IllegalArgumentException: Property 'dataSource' is required at org.springframework.jdbc.support.JdbcAccessor.afterPropertiesSet(JdbcAccessor.java:135) at org.springframework.jdbc.core.JdbcTemplate.<init>(JdbcTemplate.java:169) at cn.itcast.travel.dao.impl.UserDaoImpl.<init>(UserDaoImpl.java:10) at cn.itcast.travel.service.impl.UserServiceImpl.<init>(UserServiceImpl.java:9) at cn.itcast.travel.web.servlet.RegistUserServlet.doPost(RegistUserServlet.java:35) at javax.servlet.http.HttpServlet.service(HttpServlet.java:647) at javax.servlet.http.HttpServlet.service(HttpServlet.java:728) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:936) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1004) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589) at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748) ``` 各位，我把项目上传到了百度云，里面的代码我都已经写好了，只要启动项目，在注册页面上填写注册信息，点击提交，控制台就会报错。数据库的代码就在项目的travel.sql文件中，感兴趣有时间的可以帮忙看一下我代码究竟那里出错了，不感兴趣的可以忽略这段话，如果不是实在没有头绪，我也不会做伸手党，这已经是第二天了，今天在解决不了，就要跳过项目学框架了。谢谢各位啦链接：https://pan.baidu.com/s/1KImj8iaxV9xy-cv5ri0LXg 提取码：fzwk 复制这段内容后打开百度网盘手机App，操作更方便哦

Tomcat启动时的问题: 本地开发环境Tomcat5+jdk1.4 服务器环境 Tomcat5.5+jdk1.5 代码在本地运行无异常，编译之后放到服务器上，启动Tomcat的时候报错.......无语了 2010-06-29 09:45:17-[ERROR]-Context initialization failed org.springframework.beans.factory.CannotLoadBeanClassException: Error loading class [com.ccit.csm.preaccepted.dao.impl.BBLinodeQueryOrderDaoImpl] for bean with name 'bbLinodeQueryOrderDao' defined in class path resource [com/ccit/csm/preaccepted/daoContext-preaccepted.xml]: problem with class file or dependent class; nested exception is java.lang.ClassFormatError: com/ccit/csm/preaccepted/dao/BBLinodeQueryOrderDao (Extra bytes at the end of the class file) Caused by: java.lang.ClassFormatError: com/ccit/csm/preaccepted/dao/BBLinodeQueryOrderDao (Extra bytes at the end of the class file) at java.lang.ClassLoader.defineClass0(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:539) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:123) at org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:1634) at org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:860) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1307) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1189) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:302) at java.lang.ClassLoader.defineClass0(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:539) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:123) at org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:1634) at org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:860) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1307) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1189) at org.springframework.util.ClassUtils.forName(ClassUtils.java:201) at org.springframework.beans.factory.support.AbstractBeanDefinition.resolveBeanClass(AbstractBeanDefinition.java:327) at org.springframework.beans.factory.support.AbstractBeanFactory.resolveBeanClass(AbstractBeanFactory.java:1066) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:282) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:352) at org.springframework.web.context.support.AbstractRefreshableWebApplicationContext.refresh(AbstractRefreshableWebApplicationContext.java:156) at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:246) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:184) at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:49) at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3827) at org.apache.catalina.core.StandardContext.start(StandardContext.java:4343) at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:823) at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:807) at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:595) at org.apache.catalina.core.StandardHostDeployer.install(StandardHostDeployer.java:277) at org.apache.catalina.core.StandardHost.install(StandardHost.java:832) at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:701) at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:432) at org.apache.catalina.startup.HostConfig.start(HostConfig.java:983) at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:349) at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1091) at org.apache.catalina.core.StandardHost.start(StandardHost.java:789) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1083) at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:478) at org.apache.catalina.core.StandardService.start(StandardService.java:480) at org.apache.catalina.core.StandardServer.start(StandardServer.java:2313) at org.apache.catalina.startup.Catalina.start(Catalina.java:556) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:324) at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:287) at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:425) 2010-6-29 9:45:17 org.apache.catalina.core.StandardContext start 严重: Error listenerStart 谢谢了

java socket 长连接奇怪的问题: 我有一个类，负责通过SOCKET长连接与服务器端通讯。这个循环读取一个队列来发送。问题来了，在本类的MAIN方法中向队列中添加数据，就可以发送出去，在SERVLET中，通过HTTP请求添加，就是发送不出去！请大家帮忙看看，谢谢。下面是这个主要类的代码。 /** * */ package com.dianshangwang.lianhepayfront.service; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.io.PrintWriter; import java.io.UnsupportedEncodingException; import java.net.InetSocketAddress; import java.net.Socket; import java.net.SocketException; import java.util.HashMap; import java.util.LinkedList; import java.util.Map; import java.util.Queue; import org.apache.log4j.BasicConfigurator; import org.apache.log4j.Logger; import com.dianshangwang.lianhepayfront.global.Config; import com.google.gson.JsonObject; import com.google.gson.JsonParser; /** * @author lay * @date 2013年11月4日 */ public class IcardpayClient { private static Logger log = Logger.getLogger(IcardpayClient.class); private static Socket socket; private static BufferedReader reader; private static PrintWriter writer; private static Thread sendThread; private static Thread receiveThread; private static Thread monitorThread; private static boolean isRunning = false; /** * 心跳计数器若此值与当前时间戳值小于60000则认定断线，进行重联操作 */ private static Long heartbeatTimestamp = System.currentTimeMillis(); private static IcardpayClient instance = new IcardpayClient(); private IcardpayClient() { } public static IcardpayClient getInstance() { return instance; } public static void main(String[] args) { BasicConfigurator.configure(); IcardpayClient client = new IcardpayClient(); client.start(); MsgQueue.sendQueue.add("{\"agentNo\":\"A10342hp\",\"tradeType\":\"256\",\"sessionId\":\"1\"}"); } public void start() { init(); sendThread = new Thread(new SendThread());// 启动读线程 receiveThread = new Thread(new ReceiveThread());// 启动收线程 monitorThread = new Thread(new MonitorThread()); // 启动监视线程 sendThread.setName("icardpay-send-thread"); receiveThread.setName("icardpay-receive-thread"); monitorThread.setName("icardpay-monitor-thread"); // sendThread.setDaemon(true); // receiveThread.setDaemon(true); // monitorThread.setDaemon(true); sendThread.start(); log.info("SOCKET发送线程开启！"); receiveThread.start(); log.info("SOCKET接收线程开启！"); // monitorThread.start(); // log.info("SOCKET监视线程开启！"); } public void restart() { stop(); init(); } public void stop() { isRunning = false; } private void init() { socket = new Socket(); try { socket.setKeepAlive(true); socket.connect(new InetSocketAddress(Config.icardpayHost, Config.icardpayPort)); reader = new BufferedReader(new InputStreamReader(socket.getInputStream(), "UTF-8")); writer = new PrintWriter(socket.getOutputStream()); heartbeatTimestamp = System.currentTimeMillis(); log.info("已创建与支付通的SOCKET连接！"); isRunning = true; } catch (SocketException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (UnsupportedEncodingException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } public void write(String msg) { writer.println(msg); writer.flush(); log.info(Thread.currentThread().getName() + "发送：" + msg); } private String read() throws IOException { String msg = reader.readLine(); if (msg != null) { log.info("接收：" + msg); } return msg; } class SendThread implements Runnable { @Override public void run() { while (isRunning) { if (!MsgQueue.sendQueue.isEmpty()) { String v = MsgQueue.sendQueue.poll(); write(v); } try { Thread.sleep(300); } catch (InterruptedException e) { e.printStackTrace(); } } } } class ReceiveThread implements Runnable { @Override public void run() { while (isRunning) { String content = null; try { content = read(); } catch (IOException e1) { log.error("SOCKET读取异常，将重新启动。。。", e1); restart(); continue; } if (null == content || content == "") { continue; } JsonObject obj = new JsonParser().parse(content).getAsJsonObject(); if (obj.has("tradeType") && "0".equals(obj.get("tradeType").getAsString())) { // 收到心跳包, 刷新计数器 heartbeatTimestamp = System.currentTimeMillis(); continue; } if (!obj.has("sessionId")) { log.info("收到未标识的包：" + obj.toString()); continue; } String id = obj.get("sessionId").getAsString(); if (MsgQueue.listeners.containsKey(id)) { MsgQueue.listeners.get(id).received(content); MsgQueue.listeners.remove(id); } else { log.info("接收到过期包：" + content); } try { Thread.sleep(100); } catch (InterruptedException e) { // 忽略 } } } } class MonitorThread implements Runnable { String heartbeat = "{\"agentNo\":\"A10342hp\",\"tradeType\":\"0\"}"; @Override public void run() { while (isRunning) { if (System.currentTimeMillis() - heartbeatTimestamp >= 60000) { // SOCKET已失效 restart(); } // 发送心跳包 write(heartbeat); try { Thread.sleep(5000); } catch (InterruptedException e) { // 忽略 } } } } }

class file editor source not found: tomcat 启动时控制台输出的：信息: The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: C:\Program Files\Java\jdk1.6.0_39\bin;C:\Windows\Sun\Java\bin;C:\Windows\system32;C:\Windows;C:\Program Files\Java\jdk1.6.0_39\jre\bin;C:/Program Files/Java/jre6/bin/client;C:/Program Files/Java/jre6/bin;C:/Program Files/Java/jre6/lib/i386;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\;C:\Program Files\ATI Technologies\ATI.ACE\Core-Static;C:\Program Files\Java\jdk1.6.0_39bin;C:\eclipse;;.2015-1-11 23:11:50 org.apache.coyote.http11.Http11Protocol init2015-1-11 23:11:51 org.apache.catalina.loader.WebappClassLoader validateJarFile 信息: validateJarFile(D:\workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\OrderSystem\WEB-INF\lib\javaee_no_persistence.jar) - jar not loaded. See Servlet Spec 2.3, section 9.7.2. Offending class: javax/servlet/Servlet.class Action :List userList =userService.getUserList(); 执行这句是报：class file editor source not found 根据代码提示： throw new IllegalArgumentException("The " + methodName + "() is not defined in action " + getAction().getClass() + ""); 请高手详细点指点....谢谢

it doesn't contain soffice.bin: F:\openoffice: 用jodconverter启动openoffice时报 invalid officeHome: it doesn't contain soffice.bin: F:\openoffice 启动代码如下，有那么大神可以帮我解答哈谢谢 /** * 连接OpenOffice.org 并且启动OpenOffice.org * * @return */ public OfficeManager getOfficeManager() { DefaultOfficeManagerConfiguration config = new DefaultOfficeManagerConfiguration(); // 获取OpenOffice.org 3的安装目录 String officeHome = "F:\\openoffice"; config.setOfficeHome(officeHome); // 启动OpenOffice的服务 OfficeManager officeManager = config.buildOfficeManager(); officeManager.start(); return officeManager; }

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花了20分钟，给女朋友们写了一个web版群聊程序: 参考博客 [1]https://www.byteslounge.com/tutorials/java-ee-html5-websocket-example

爬虫福利二之妹子图网MM批量下载: 爬虫福利一：27报网MM批量下载点击看了本文，相信大家对爬虫一定会产生强烈的兴趣，激励自己去学习爬虫，在这里提前祝：大家学有所成！目标网站：妹子图网环境：Python3.x 相关第三方模块：requests、beautifulsoup4 Re：各位在测试时只需要将代码里的变量 path 指定为你当前系统要保存的路径，使用 python xxx.py 或IDE运行即可。

字节跳动视频编解码面经: 引言本文主要是记录一下面试字节跳动的经历。三四月份投了字节跳动的实习（图形图像岗位），然后hr打电话过来问了一下会不会opengl，c++，shador，当时只会一点c++，其他两个都不会，也就直接被拒了。七月初内推了字节跳动的提前批，因为内推没有具体的岗位，hr又打电话问要不要考虑一下图形图像岗，我说实习投过这个岗位不合适，不会opengl和shador，然后hr就说秋招更看重基础。我当时

Java学习的正确打开方式: 在博主认为，对于入门级学习java的最佳学习方法莫过于视频+博客+书籍+总结，前三者博主将淋漓尽致地挥毫于这篇博客文章中，至于总结在于个人，实际上越到后面你会发现学习的最好方式就是阅读参考官方文档其次就是国内的书籍，博客次之，这又是一个层次了，这里暂时不提后面再谈。博主将为各位入门java保驾护航，各位只管冲鸭！！！上天是公平的，只要不辜负时间，时间自然不会辜负你。何谓学习？博主所理解的学习，它

程序员必须掌握的核心算法有哪些？: 由于我之前一直强调数据结构以及算法学习的重要性，所以就有一些读者经常问我，数据结构与算法应该要学习到哪个程度呢？，说实话，这个问题我不知道要怎么回答你，主要取决于你想学习到哪些程度，不过针对这个问题，我稍微总结一下我学过的算法知识点，以及我觉得值得学习的算法。这些算法与数据结构的学习大多数是零散的，并没有一本把他们全部覆盖的书籍。下面是我觉得值得学习的一些算法以及数据结构，当然，我也会整理一些看过

大学四年自学走来，这些私藏的实用工具/学习网站我贡献出来了: 大学四年，看课本是不可能一直看课本的了，对于学习，特别是自学，善于搜索网上的一些资源来辅助，还是非常有必要的，下面我就把这几年私藏的各种资源，网站贡献出来给你们。主要有：电子书搜索、实用工具、在线视频学习网站、非视频学习网站、软件下载、面试/求职必备网站。注意：文中提到的所有资源，文末我都给你整理好了，你们只管拿去，如果觉得不错，转发、分享就是最大的支持了。一、电子书搜索对于大部分程序员...

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