java中Object.equals()简单用法

/*
equals（）方法默认的比较两个对象的引用！
*/
class Child {int num;public Child(int x){num = x;}//人文的抛出运行时异常的好处是：可以自定义错误信息！/*public boolean equals(Object o) throws ClassCastException{if(!(o instanceof Child)) throw new ClassCastException("中文提示：类型错误");Child ch = (Child) o;return num == ch.num ;}*//*Exception in thread "main" java.lang.ClassCastException: 中文提示：类型错误at Child.equals(PC.java:8)at PC.main(PC.java:17)*/public boolean equals(Object o){Child ch = (Child) o;return num == ch.num ;}/*Exception in thread "main" java.lang.ClassCastException: java.lang.Integer cannotbe cast to Childat Child.equals(PC.java:14)at PC.main(PC.java:22)*/
}public class PC{public static void main(String[] args){Child p1 = new Child(11);if(p1.equals(new Integer(11)))System.out.println("true");System.out.println("这句话是否执行？");// 如果异常得到了处理， 那么这句话就会执行，否则就不会被执行！}
}