java 一维和二维数组的拷贝问题

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本文详细介绍了Java中一维和二维数组的浅拷贝与深拷贝操作，并通过具体示例展示了不同拷贝方式下数组元素的变化情况。

package com.itjob.test2;

import java.util.Arrays;

public class ArrayCopy {

/**
* @author x521
* @createDate 2008-5-21
* 一维数组的拷贝---浅拷贝
*/
public static void main(String[] args) {
  copyArray();
  copyObject();
}

public static void copyArray() {
  int[] a = new int[5];
  int[] b = new int[6];

  a[0] = 12;
  a[1] = 45;
  a[2] = 90;
  a[3] = 100;
  a[4] = 160;

  for(int aa : a) {
   System.out.print(aa + " ");
  }

  System.out.println("/n ---");
  System.arraycopy(a, 0, b, 1, a.length);

  for(int bb : b) {
   System.out.print(bb + " ");
  }
  System.out.println();

  System.out.println("************");
  a[4] = 200;

  for(int bbb : b) {
   System.out.print(bbb + " ");
  }

  System.out.println("/n*************");

  for(int aaa : a) {
   System.out.print(aaa + " ");
  }

  System.out.println("/n****************");
}

public static void copyObject() {
  TestCopy[] tc1 = new TestCopy[2];
  TestCopy[] tc2 = new TestCopy[2];
  tc1[0] = new TestCopy();
  tc1[1] = new TestCopy();
  tc1[0].setName("h1");
  tc1[1].setName("h2");

  for(TestCopy co : tc1) {

   System.out.print(co.getName() + " ");
  }

  System.out.println();

  System.arraycopy(tc1, 0, tc2, 0, tc1.length);

  for(TestCopy tc : tc2) {
   System.out.print(tc.getName() + " ");
  }

  //重新设置tc2[1]的值后 tc1[1]的值也发生了变化
  // 这种情况属于数组的浅拷贝问题

  tc2[1].setName("hello");

  System.out.println();

  for(TestCopy tc11 : tc1) {
   System.out.print(tc11.getName() + " ");
  }
  System.out.println("/n----");
}

}

class TestCopy {
private String name;

public void setName(String name) {
this.name = name;
}

public String getName() {
return name;
}
}

// output:

12 45 90 100 160
---
0 12 45 90 100 160
************
0 12 45 90 100 160
*************
12 45 90 100 200
****************
h1 h2
h1 h2
h1 hello
----

/*
* TwoArrayCopy.java
*/

package com.itjob.test2;

import java.util.Arrays;

public class TwoArrayCopy {

/**
* @author x521
* @createDate 2008-5-21
* 二维数组的拷贝---浅拷贝
*/
public static void main(String[] args) {
  int[][] a = new int[2][3];
  int[][] b = new int[2][3];
  for(int i=0; i<2; i++) {
   for(int j=0; j<3; j++) {
    System.out.print(a[i][j] + " ");
   }
   System.out.println();
  }

  System.out.println("****************");
  a[0][2] = 100;

  for(int[] aa : a) {
   System.out.println(Arrays.toString(aa));
  }

  System.out.println("****************");

  System.arraycopy(a, 0, b, 0, a.length);

  //修改a[1][2]的值，并且b[1][2]的值也被改变

  a[1][2] = 500;
  for(int[] bb : b) {
   System.out.println(Arrays.toString(bb));
  }

  System.out.println("****************");

  for(int[] aa : a) {
   System.out.println(Arrays.toString(aa));
  }
}

}

//output:

0 0 0
0 0 0
****************
[0, 0, 100]
[0, 0, 0]
****************
[0, 0, 100]
[0, 0, 500]
****************
[0, 0, 100]
[0, 0, 500]

/*
* TwoArrayCopy1.java
*/

package com.itjob.test2;

import java.util.Arrays;

public class TwoArrayCopy1 {

/**
* @author x521
* @createDate 2008-5-21
* 二维数组的拷贝---深拷贝
*/
public static void main(String[] args) {
  int[][] a = new int[2][3];
  int[][] b = new int[2][3];
  a[0][0] = 12;
  a[0][1] = 23;
  a[0][2] = 20;

  a[1][0] = 15;
  a[1][1] = 11;
  a[1][2] = 12;

  for(int[] aa : a) {
   System.out.println(Arrays.toString(aa));
  }

  System.out.println("**************");

  for(int i=0; i<a.length; i++) {
   for(int j=0; j<a[i].length; j++) {
    b[i][j] = a[i][j];
   }
  }

  for(int[] bb : b) {
   System.out.println(Arrays.toString(bb));
  }

  System.out.println("**************");

  //修改b[0][2]的值而 a[0][2]的值没有被改变
  //这属于多维数组的深拷贝

  b[0][2] = 100;

  for(int[] aaa : a) {
   System.out.println(Arrays.toString(aaa));
  }

  System.out.println("**************");

  for(int[] bbb : b) {
   System.out.println(Arrays.toString(bbb));
  }

  System.out.println("**************");
}

}

//output :

[12, 23, 20]
[15, 11, 12]
**************
[12, 23, 20]
[15, 11, 12]
**************
[12, 23, 20]
[15, 11, 12]
**************
[12, 23, 100]
[15, 11, 12]
**************