Class not implements Cloneable will cause CloneNotSupportedException

houzhizhen

于 2019-04-10 09:16:00 发布

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分类专栏： java

本文链接：https://blog.youkuaiyun.com/houzhizhen/article/details/89173659

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本文通过两个测试案例，深入探讨了Java中实现克隆模式的方法和注意事项。首先，当类实现了Cloneable接口并正确覆盖clone方法时，可以成功创建对象的浅拷贝，修改拷贝对象不会影响原始对象。然而，若未实现Cloneable接口直接调用super.clone()，将抛出CloneNotSupportedException异常。本文旨在帮助读者理解克隆模式的正确使用方式。

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The test case using jdk 1.8.

class C implements Cloneable

class C implements Cloneable {
    int id;

    public C(int id) {
        this.id = id;
    }
    @Override
    public C clone() throws CloneNotSupportedException {
        return (C)super.clone();
    }
}
public class CloneTest {

    @Test
    public void test1() throws CloneNotSupportedException {
        C c1 = new C(100);
        C c2 = c1.clone();
        System.out.println("c1:" + c1.id);
        System.out.println("c2:" + c2.id);
        c2.id = 101;
        System.out.println("c1:" + c1.id);
        System.out.println("c2:" + c2.id);
    }
}

Run the test case, it will print the following content.

c1:100
c2:100
c1:100
c2:101

Class not implements Cloneable

class C {
    int id;

    public C(int id) {
        this.id = id;
    }
    @Override
    public C clone() throws CloneNotSupportedException {
        return (C)super.clone();
    }
}
public class CloneTest {

    @Test
    public void test1() throws CloneNotSupportedException {
        C c1 = new C(100);
        C c2 = c1.clone();
        System.out.println("c1:" + c1.id);
        System.out.println("c2:" + c2.id);
        c2.id = 101;
        System.out.println("c1:" + c1.id);
        System.out.println("c2:" + c2.id);
    }
}

Run the test case, it will print the following content.


java.lang.CloneNotSupportedException: Item11.C

	at java.lang.Object.clone(Native Method)
	at Item11.C.clone(CloneTest.java:13)
	at Item11.CloneTest.test1(CloneTest.java:22)
	...