Question

我试图了解Object类的clone（）方法的工作原理。 Object类中的注释表示＆＃39; 此方法执行＆＃34;浅拷贝＆＃34;这个对象，而不是＆＃34;深拷贝＆＃34; 。操作＆＃39;

以下是我对Shallow＆amp; amp;的理解深拷贝..

浅拷贝尽可能少复制。浅的副本   集合是集合结构的副本，而不是元素。   通过浅拷贝，两个集合现在共享个人   元件。

深层副本重复所有内容。集合的深层副本是两个   包含原始集合中所有元素的集合   复制。

因此，如果我克隆一个Object并修改它在克隆上的任何可变元素，那么同样应该反映在创建克隆的第一个对象上，因为它们共享相同的内存。为了测试这个，我创建了3个类......

一个简单的pojo ..

package test.clone;

import java.util.Arrays;

public class Misc implements Cloneable{
    private String value;

    public Misc(String value) {
        super();
        this.value = value;
    }

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }

    @Override
    public String toString() {
        return "Misc [value=" + value + "]";
    }


    protected Misc clone() throws CloneNotSupportedException{
        return (Misc)super.clone();
    }

}

需要克隆的类..

package test.clone;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;


public class Victim implements Cloneable{
    private String name = "Renjith";
    private String[] educationList = {"EDU_1", "EDU_2", "EDU_3", "EDU_4"};
    private Misc[] miscList = {new Misc("1"), new Misc("2")};
    private List<Misc> miscList2 = new ArrayList<Misc>(Arrays.asList(miscList));

    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String[] getEducationList() {
        return educationList;
    }
    public void setEducationList(String[] educationList) {
        this.educationList = educationList;
    }

    protected Victim clone() throws CloneNotSupportedException{
        return (Victim)super.clone();
    }
    public Misc[] getMiscList() {
        return miscList;
    }
    public void setMiscList(Misc[] miscList) {
        this.miscList = miscList;
    }


    public List<Misc> getMiscList2() {
        return miscList2;
    }
    public void setMiscList2(List<Misc> miscList2) {
        this.miscList2 = miscList2;
    }
    @Override
    public String toString() {
        return "Victim [name=" + name + ", educationList="
                + Arrays.toString(educationList) + ", miscList="
                + Arrays.toString(miscList) + ", miscList2=" + miscList2 + "]";
    }



}

进行克隆的主要类......和修改......

public class Main {

    public static void main(String[] args) throws CloneNotSupportedException {
        Victim victim = new Victim();

        System.out.println(victim);

        Victim secondVictim = victim.clone();

        String[] educationList = {"EDU_1_mod", "EDU_2_mod", "EDU_3_mod", "EDU_4_mod"};
        Misc[] miscList = {new Misc("3"), new Misc("4")};
        List<Misc> miscList2 = new ArrayList<Misc>(Arrays.asList(miscList));

        secondVictim.setEducationList(educationList);
        secondVictim.setMiscList(miscList);
        secondVictim.setMiscList2(miscList2);

        System.out.println(secondVictim);

        System.out.println(victim);
    }

}

我期待输出如下......

受害者[name = Renjith，educationList = [EDU_1，EDU_2，EDU_3，EDU_4]， miscList = [Misc [value = 1]，Misc [value = 2]]，miscList2 = [Misc [value = 1]，杂项[value = 2]]]受害者[name = Renjith，educationList = [EDU_1_mod， EDU_2_mod，EDU_3_mod，EDU_4_mod]，miscList = [Misc [value = 3]，Misc [value = 4]]，miscList2 = [Misc [value = 3]，Misc [value = 4]]]受害者 [name = Renjith，educationList = [EDU_1，EDU_2，EDU_3，EDU_4]， miscList = [杂项[值= 3 ]，杂项[值= 4 ]]，miscList2 = [杂项[值= 3 ]，其他[值= 4 ]]]

但我得到了......

受害者[name = Renjith，educationList = [EDU_1，EDU_2，EDU_3，EDU_4]， miscList = [Misc [value = 1]，Misc [value = 2]]，miscList2 = [Misc [value = 1]，杂项[value = 2]]]受害者[name = Renjith，educationList = [EDU_1_mod， EDU_2_mod，EDU_3_mod，EDU_4_mod]，miscList = [Misc [value = 3]，Misc [value = 4]]，miscList2 = [Misc [value = 3]，Misc [value = 4]]]受害者 [name = Renjith，educationList = [EDU_1，EDU_2，EDU_3，EDU_4]， miscList = [Misc [ value = 1 ]，其他[值= 2 ]]，miscList2 = [其他[值= 1 ]，其他[值= 2 ]]]

任何人都可以告诉我这有什么问题吗？

我已经完成了Understanding Object.clone() in Java，但仍然无法理解......

Answer 1

您没有修改列表/数组，而是用新引用替换它们。尝试像这样更新你的setter：

public void setMiscList(Misc[] miscList) {
    this.miscList[0] = miscList[0];
    this.miscList[1] = miscList[1];
}

public void setMiscList2(List<Misc> miscList2) {
    this.miscList2.set(0, miscList2.get(0));
    this.miscList2.set(1, miscList2.get(1));
}

这应修改共享对象，从而产生预期的输出。

object.clone（）究竟是如何在java中工作的？

1 个答案: