CloneNotSupportedException的解决方案 + Object的clone方法分析-编程知识

CloneNotSupportedException的解决方案 + Object的clone方法分析

CloneNotSupportedException的解决方案

引入问题：

在一次测试clone方法时，D类Override了Object类的clone方法

public class D {private Integer A1;private Integer A2;public D() {}public D(Integer a1, Integer a2 {A1 = a1;A2 = a2;}@Overrideprotected Object clone() throws CloneNotSupportedException {return super.clone();}
}
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在测试类中执行clone方法报错了

public class Test5 {public static void main(String[] args) {D p  = new D();D p2 = null;try {p2 = (D)p.clone();} catch (CloneNotSupportedException e) {e.printStackTrace();}System.out.println(p == p2);}}
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在这里插入图片描述

抛出了 CloneNotSupportedException

寻找原因：

既然是重写自Object的clone方法，那么去看看Object对该方法的定义：

protected native Object clone() throws CloneNotSupportedException;
1

其中对于异常抛出的描述如下：

Throws:
CloneNotSupportedException – if the object’s class does not support the Cloneable interface. Subclasses that override the clone method can also throw this exception to indicate that an instance cannot be cloned.

如果对象的class不实现Cloneable接口，子类重写clone方法会同样抛出异常表示实例不能被克隆；

哦？

那不意思就是说：你要不父类实现Cloneable接口，要不就子类实现Cloneable

两个测试代码：

测试1：在父类上实现Cloneable接口

public class TestClone {public static void main(String[] args) throws CloneNotSupportedException {Father father = new Father();Father fatherClone = (Father) father.clone();Son son = new Son();Son sonClone = (Son) son.clone();System.out.println(father==fatherClone);System.out.println(son==sonClone);}}class Father implements Cloneable{private Integer f1;private Integer f2;public Father() {}public Father(Integer f1, Integer f2) {this.f1 = f1;this.f2 = f2;}@Overrideprotected Object clone() throws CloneNotSupportedException {return super.clone();}
}class Son extends Father{private Integer s1;private Integer s2;public Son() {}public Son(Integer s1, Integer s2) {this.s1 = s1;this.s2 = s2;}@Overrideprotected Object clone() throws CloneNotSupportedException {return super.clone();}
}
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不出意外，没有任何问题

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测试2：在子类上实现Cloneable接口

public class TestClone {public static void main(String[] args) throws CloneNotSupportedException {
//        Father father = new Father();
//        Father fatherClone = (Father) father.clone();Son son = new Son();Son sonClone = (Son) son.clone();//        System.out.println(father==fatherClone);System.out.println(son==sonClone);}}class Father {private Integer f1;private Integer f2;public Father() {}public Father(Integer f1, Integer f2) {this.f1 = f1;this.f2 = f2;}@Overrideprotected Object clone() throws CloneNotSupportedException {return super.clone();}
}class Son extends Father implements Cloneable{private Integer s1;private Integer s2;public Son() {}public Son(Integer s1, Integer s2) {this.s1 = s1;this.s2 = s2;}@Overrideprotected Object clone() throws CloneNotSupportedException {return super.clone();}
}
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