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标题: 【广州】【原创】浅克隆和深度克隆 [打印本页]

作者: yqw_gz_java 时间: 2019-12-3 14:14
标题: 【广州】【原创】浅克隆和深度克隆
本帖最后由 yqw_gz_java 于 2019-12-3 15:07 编辑

在实际编程过程中，我们常常要遇到这种情况：有一个对象A，在某一时刻A中已经包含了一些有效值，此时可能会需要一个和A完全相同新对象B，并且此后对B任何改动都不会影响到A中的值，也就是说，A与B是两个独立的对象，但B的初始值是由A对象确定的。这里就要用到java中克隆的知识了.
克隆包括:浅克隆  和深度克隆
一 :如果 A对象的组成都是基本数据类型,只要浅克隆即可.
尺寸类:
[Java] 纯文本查看 复制代码
package cn.yqw.shallowclone;

/**
* @author: 杨钦炜
* @mail 4024081418@qq.com
* @create: 2019-12-03 14:47
*/
public class Measurement implements Cloneable {

public int length;
public int width;

public Measurement(int length, int width) {
      this.length = length;
      this.width = width;
}

@Override
public String toString() {
      return "Measurement{" +
            "length=" + length +
            ", width=" + width +
            '}';
}

@Override
protected Measurement clone() {
      Measurement clone = null;
      try {
         clone = (Measurement) super.clone();
      } catch (CloneNotSupportedException e) {
         e.printStackTrace();
      }

      return clone;
}

public int getLength() {
      return length;
}

public void setLength(int length) {
      this.length = length;
}

public int getWidth() {
      return width;
}

public void setWidth(int width) {
      this.width = width;
}
}

测试类:
[Java] 纯文本查看 复制代码
package cn.yqw.shallowclone;

/**
* @author: 杨钦炜
* @mail 4024081418@qq.com
* @create: 2019-12-03 14:52
*/
public class Test1 {

public static void main(String[] args) {
      Measurement m1 = new Measurement(10, 20);
      Measurement  m2 =  m1.clone();
      m2.length=128;
      m2.width=100;
      System.out.println("m2:==>"+m2);
      System.out.println("m1:==>"+m1);

}
}

输出效果:
[AppleScript] 纯文本查看 复制代码
C:\java8\bin\java.exe "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA 2019.2.4\lib\idea_rt.jar=2098:C:\Program Files\JetBrains\IntelliJ IDEA 2019.2.4\bin" -Dfile.encoding=UTF-8 -classpath C:\java8\jre\lib\charsets.jar;C:\java8\jre\lib\deploy.jar;C:\java8\jre\lib\ext\access-bridge-64.jar;C:\java8\jre\lib\ext\cldrdata.jar;C:\java8\jre\lib\ext\dnsns.jar;C:\java8\jre\lib\ext\jaccess.jar;C:\java8\jre\lib\ext\jfxrt.jar;C:\java8\jre\lib\ext\localedata.jar;C:\java8\jre\lib\ext\nashorn.jar;C:\java8\jre\lib\ext\sunec.jar;C:\java8\jre\lib\ext\sunjce_provider.jar;C:\java8\jre\lib\ext\sunmscapi.jar;C:\java8\jre\lib\ext\sunpkcs11.jar;C:\java8\jre\lib\ext\zipfs.jar;C:\java8\jre\lib\javaws.jar;C:\java8\jre\lib\jce.jar;C:\java8\jre\lib\jfr.jar;C:\java8\jre\lib\jfxswt.jar;C:\java8\jre\lib\jsse.jar;C:\java8\jre\lib\management-agent.jar;C:\java8\jre\lib\plugin.jar;C:\java8\jre\lib\resources.jar;C:\java8\jre\lib\rt.jar;C:\Users\yqw\IdeaProjects\jishutie\target\classes cn.yqw.shallowclone.Test1
m2:==>Measurement{length=128, width=100}
m1:==>Measurement{length=10, width=20}
Process finished with exit code 0

从上面测试效果来看,两个对象已经是互不影响了,接着看下面的列子
现在有学生类,和地址类,clone 一个学生,然后修改地址对象
学生类代码如下:
[Java] 纯文本查看 复制代码
package cn.yqw.clone;

/**
* @author: 杨钦炜
* @mail 4024081418@qq.com
* @create: 2019-12-03 13:56
*/
public class Student implements Cloneable {

public String studentname;
public Address address;

public Student(String studentname, Address address) {
      this.studentname = studentname;
      this.address = address;
}

@Override
protected Student clone(){

      Student clone = null;
      try {
         clone = (Student) super.clone();
      } catch (CloneNotSupportedException e) {
         e.printStackTrace();
      }

      return clone;
}

@Override
public String toString() {
      return "Student{" +
            "studentname='" + studentname + '\'' +
            ", address=" + address +
            '}';
}
}

地址类代码如下:
[Java] 纯文本查看 复制代码
package cn.yqw.clone;

/**
* @author: 杨钦炜
* @mail 4024081418@qq.com
* @create: 2019-12-03 13:57
*/
public class Address  {
/**
   * 简要
   */
public String brief;
/**
   * 详情
   */
public String details;

public Address(String brief, String details) {
      this.brief = brief;
      this.details = details;
}

@Override
public String toString() {
      return "Address{" +
            "brief='" + brief + '\'' +
            ", details='" + details + '\'' +
            '}';
}
}

测试类代码如下
[Java] 纯文本查看 复制代码
package cn.yqw.clone;

/**
* @author: 杨钦炜
* @mail 4024081418@qq.com
* @create: 2019-12-03 13:58
*/
public class Test {

public static void main(String[] args) {
      Student student = new Student("学生一",new Address("湖南","湖南省邵阳市新宁县丰田乡"));
      Student clone = student.clone();
      System.out.println(clone);

      clone.address.brief="广州";
      clone.address.details="广东省广州市天河区";

      System.out.println("-----------------------------------");
      System.out.println("clone:===>"+clone);
      System.out.println("student:===>"+student);

}
}

输出效果
Student{studentname='学生一', address=Address{brief='湖南', details='湖南省邵阳市新宁县丰田乡'}}
-----------------------------------
clone:===>Student{studentname='学生一', address=Address{brief='广州', details='广东省广州市天河区'}}
student:===>Student{studentname='学生一', address=Address{brief='广州', details='广东省广州市天河区'}}
从上面的测试来看,对学生二做修改影响到了学生一,这不是我们想要的结果,接下来就要用我深度克隆来解决这个问题
修改地址类:
[Java] 纯文本查看 复制代码
package cn.yqw.clone;

/**
* @author: 杨钦炜
* @mail 4024081418@qq.com
* @create: 2019-12-03 13:57
*/
public class Address implements  Cloneable{
/**
   * 简要
   */
public String brief;
/**
   * 详情
   */
public String details;

public Address(String brief, String details) {
      this.brief = brief;
      this.details = details;
}

@Override
protected Address  clone()  {
      Address clone = null;
      try {
         clone = (Address) super.clone();
      } catch (CloneNotSupportedException e) {
         e.printStackTrace();
      }
      return clone;
}

@Override
public String toString() {
      return "Address{" +
            "brief='" + brief + '\'' +
            ", details='" + details + '\'' +
            '}';
}
}

学生类修改如下:

[Java] 纯文本查看 复制代码

package cn.yqw.clone;



/**

 * @author: 杨钦炜

 * @mail 4024081418@qq.com

 * @create: 2019-12-03 13:56

 */

public class Student implements Cloneable {



    public String studentname;

    public Address address;



    public Student(String studentname, Address address) {

        this.studentname = studentname;

        this.address = address;

    }



    @Override

    protected Student clone() {



        Student clone = null;

        try {

            clone = (Student) super.clone();

        } catch (CloneNotSupportedException e) {

            e.printStackTrace();

        }

        clone.address = clone.address.clone();

        return clone;

    }





    @Override

    public String toString() {

        return "Student{" +

                "studentname='" + studentname + '\'' +

                ", address=" + address +

                '}';

    }

}

测测试结果:

[AppleScript] 纯文本查看 复制代码

Student{studentname='学生一', address=Address{brief='湖南', details='湖南省邵阳市新宁县丰田乡'}}

-----------------------------------

clone:===>Student{studentname='学生一', address=Address{brief='广州', details='广东省广州市天河区'}}

student:===>Student{studentname='学生一', address=Address{brief='湖南', details='湖南省邵阳市新宁县丰田乡'}}

总结:当被克隆的对象存在引用类型的属性,就要用到深度克隆.

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