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;
    }

    @Override
    protected 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;
    }

    @Override
    protected 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;
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }
}
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不出意外，没有任何问题

在这里插入图片描述

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;
    }

    @Override
    protected 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;
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }
}
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