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import java.util.Arrays;
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/**
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* 老紫竹JAVA提高教程 - System.arraycopy方法的使用。<br>
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* <br>
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* 从指定源数组中复制一个数组,复制从指定的位置开始,<br>
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* 到目标数组的指定位置结束
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*
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* @author 老紫竹的家(java2000.net,laozizhu.com)
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*
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*/
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public class LessionSystemArraycopy {
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public static void main(String[] args) {
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// 此方位为native方法。
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// public static native void arraycopy(
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// Object src, int srcPos, Object dest,
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// int destPos, int length);
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// 初始化
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int[] ids = { 1, 2, 3, 4, 5 };
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System.out.println(Arrays.toString(ids)); // [1, 2, 3, 4, 5]
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// 测试自我复制
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// 把从索引0开始的2个数字复制到索引为3的位置上
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System.arraycopy(ids, 0, ids, 3, 2);
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System.out.println(Arrays.toString(ids)); // [1, 2, 3, 1, 2]
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// 测试复制到别的数组上
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// 将数据的索引1开始的3个数据复制到目标的索引为0的位置上
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int[] ids2 = new int[6];
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System.arraycopy(ids, 1, ids2, 0, 3);
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System.out.println(Arrays.toString(ids2)); // [2, 3, 1, 0, 0, 0]
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// 此功能要求
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// 源的起始位置+长度不能超过末尾
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// 目标起始位置+长度不能超过末尾
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// 且所有的参数不能为负数
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try {
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System.arraycopy(ids, 0, ids2, 0, ids.length + 1);
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} catch (IndexOutOfBoundsException ex) {
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// 发生越界异常,数据不会改变
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System.out.println("拷贝发生异常:数据越界。");
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}
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System.out.println(Arrays.toString(ids2)); // [2, 3, 1, 0, 0, 0]
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// 如果是类型转换问题
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Object[] o1 = { 1, 2, 3, 4.5, 6.7 };
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Integer[] o2 = new Integer[5];
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System.out.println(Arrays.toString(o2)); // [null, null, null, null, null]
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try {
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System.arraycopy(o1, 0, o2, 0, o1.length);
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} catch (ArrayStoreException ex) {
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// 发生存储转换,部分成功的数据会被复制过去
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System.out.println("拷贝发生异常:数据转换错误,无法存储。");
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}
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// 从结果看,前面3个可以复制的数据已经被存储了。剩下的则没有
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System.out.println(Arrays.toString(o2)); // [1, 2, 3, null, null]
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}
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}
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本文来自CSDN博客,转载请标明出处:http://blog.csdn.net/java2000_net/archive/2009/04/09/4059465.aspx
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