关于java package的疑惑

Question

//package com.antiy;

abstract class animal {
    public abstract void eat();
    public abstract void run();
}

class human extends animal {
    human(){}

    public  void eat(){
        System.out.println("Human eat");
    }

    public void run(){
        System.out.println("Human run");
    }
}
public class Hello {
    public static void main(String[] args){
        System.out.println("Hello");
        human o1 = new human();
        Hello.do_eat(o1); 
    }

    static void do_eat(animal o){
        o.eat();
    }
}

在Hello.java中包含如上代码，编译和运行都正常:

wangbo@wangbodeMBP:/tmp/java_project$ cat Hello.java
//package com.antiy;

abstract class animal {
    public abstract void eat();
    public abstract void run();
}

class human extends animal {
    human(){}

    public  void eat(){
        System.out.println("Human eat");
    }

    public void run(){
        System.out.println("Human run");
    }
}
public class Hello {
    public static void main(String[] args){
        System.out.println("Hello");
        human o1 = new human();
        Hello.do_eat(o1);
    }

    static void do_eat(animal o){
        o.eat();
    }
}


wangbo@wangbodeMBP:/tmp/java_project$ javac Hello.java
wangbo@wangbodeMBP:/tmp/java_project$ java Hello
Hello
Human eat

如果把package放开，编译没有问题，运行会提示human类找不到:

wangbo@wangbodeMBP:/tmp/java_project$ cat Hello.java
package com.antiy;

abstract class animal {
    public abstract void eat();
    public abstract void run();
}

class human extends animal {
    human(){}

    public  void eat(){
        System.out.println("Human eat");
    }

    public void run(){
        System.out.println("Human run");
    }
}
public class Hello {
    public static void main(String[] args){
        System.out.println("Hello");
        human o1 = new human();
        Hello.do_eat(o1);
    }

    static void do_eat(animal o){
        o.eat();
    }
}


wangbo@wangbodeMBP:/tmp/java_project$ javac Hello.java
wangbo@wangbodeMBP:/tmp/java_project$ cp Hello.class com/antiy/
wangbo@wangbodeMBP:/tmp/java_project$ java com/antiy/Hello
错误: 无法初始化主类 com.antiy.Hello
原因: java.lang.NoClassDefFoundError: com/antiy/animal

如果把package放开，把human相关的代码注释掉也可以正常运行：

wangbo@wangbodeMBP:/tmp/java_project$ cat Hello.java
package com.antiy;

abstract class animal {
    public abstract void eat();
    public abstract void run();
}

class human extends animal {
    human(){}

    public  void eat(){
        System.out.println("Human eat");
    }

    public void run(){
        System.out.println("Human run");
    }
}
public class Hello {
    public static void main(String[] args){
        System.out.println("Hello");
        //human o1 = new human();
        //Hello.do_eat(o1);
    }

    static void do_eat(animal o){
        o.eat();
    }
}


wangbo@wangbodeMBP:/tmp/java_project$ javac Hello.java
wangbo@wangbodeMBP:/tmp/java_project$ cp Hello.class com/antiy/
wangbo@wangbodeMBP:/tmp/java_project$ java com/antiy/Hello
Hello

我知道优雅的java工程不会把两个类放在一个java文件中，但是两个类放在一个java文件系统也可以支持

我的疑惑是如上代码，如果放开package为什么runtime会提示human类找不到 ？

Answer 1

你确定不放开package运行没问题？human的构造函数是私有没问题？.java的文件路径和package写的一样？