Java深度复制功能与用法实例分析

package com.yo.java;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
/**
 * Java 实现深度复制
 * @author Yo
 *
 */
public class DeepCopy implements Serializable{
  int i;
  /**
   * @param args
   * @throws IOException
   * @throws ClassNotFoundException
   */
  public static void main(String[] args) throws ClassNotFoundException, IOException {
    demo1();
    demo2();
  }
  /**
   * 深度复制，实参类必须实现Serializable接口
   * @param o
   * @return
   * @throws IOException
   * @throws ClassNotFoundException
   */
  public static Object deepCopy(Object o) throws IOException, ClassNotFoundException {
//   //先序列化，写入到流里
    ByteArrayOutputStream bo = new ByteArrayOutputStream();
    ObjectOutputStream oo = new ObjectOutputStream(bo);
    oo.writeObject(o);
    //然后反序列化，从流里读取出来，即完成复制
    ByteArrayInputStream bi = new ByteArrayInputStream(bo.toByteArray());
    ObjectInputStream oi = new ObjectInputStream(bi);
    return oi.readObject();
  }
  /**
   * 引用传递与深度复制
   * @throws ClassNotFoundException
   * @throws IOException
   */
  public static void demo1() throws ClassNotFoundException, IOException {
    System.out.println("===========未使用深度复制=========");
    DeepCopy dc1 = new DeepCopy();
    dc1.i = 1;//初始化dc1里i的值
    DeepCopy dc2 = dc1;
    dc1.i = 2;//改变dc1里i的值
    System.out.println("dc1 : " + dc1.i);
    System.out.println("dc2(引用传递) : " + dc2.i);
    System.out.println("===========使用深度复制=========");
    DeepCopy dc3 = new DeepCopy();
    dc3.i = 1;//初始化dc3里i的值
    DeepCopy dc4 = (DeepCopy)deepCopy(dc3);
    dc3.i = 2;//改变dc3里i的值
    System.out.println("dc3 : " + dc3.i);
    System.out.println("dc4(深度复制) : " + dc4.i);
  }
  /**
   * 集合的值复制与深度复制
   * @throws ClassNotFoundException
   * @throws IOException
   */
  public static void demo2() throws ClassNotFoundException, IOException {
    System.out.println("===========未使用深度复制=========");
    //创建DeepCopy对象，并初始化i的值，添加到list1集合
    DeepCopy dc = new DeepCopy();
    dc.i = 1;//初始化dc1里i的值
    List<DeepCopy> list1 = new ArrayList<DeepCopy>();
    list1.add(dc);
    //未使用深度复制
    List<DeepCopy> list2 = new ArrayList<DeepCopy>(list1);//这里与使用Collections.copy(dest, src)结果一样
    //改变list1中元素的值
    for(DeepCopy d1 : list1) {
      //改变dc1里i的值
      d1.i = 2;
    }
    //遍历list
    for(DeepCopy d1 : list1) {
      System.out.println("list1 : " + d1.i);
    }
    //遍历list2
    for(DeepCopy d2 : list2) {
      System.out.println("list2(复制） : " + d2.i);
    }
    System.out.println("===========使用深度复制后=========");
    DeepCopy dc3 = new DeepCopy();
    dc3.i = 1;//初始化dc3里i的值
    List<DeepCopy> list3 = new ArrayList<DeepCopy>();
    list3.add(dc3);
    List<DeepCopy> list4 = (List<DeepCopy>) deepCopy(list3);
    for(DeepCopy d : list3) {
      //改变dc3里i的值
      d.i = 2;
    }
    for(DeepCopy d3 : list3) {
      System.out.println("list3 : " + d3.i);
    }
    for(DeepCopy d4 : list4) {
      System.out.println("list4(深度复制）: " + d4.i);
    }
  }
}

===========未使用深度复制=========
dc1 : 2
dc2(引用传递) : 2
===========使用深度复制=========
dc3 : 2
dc4(深度复制) : 1
===========未使用深度复制=========
list1 : 2
list2(复制） : 2
===========使用深度复制后=========
list3 : 2
list4(深度复制）: 1