王杰13320675430的博客本问题需要对泛型有深刻了解,原理题主明白,只是不明白我下面说明的这个问题代码如下public class Shape implements Comparable {@Overridepublic int compareTo(Shape o) {return 0;}}public class Square extends...
weixin_39752880的博客方法想实现的功能就是传入子类...28) at com.classTest.MainTest.main(MainTest.java:15) Exception in thread "main" java.lang.NullPointerException at com.classTest.MainTest.main(MainTest.java:16) 求指教!!!