1. Simple Code Examples
System.arraycopy()
int[] arr = {1,2,3,4,5}; int[] copied = new int[10]; System.arraycopy(arr, 0, copied, 1, 5);//5 is the length to copy System.out.println(Arrays.toString(copied));
Output:
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
[0, 1, 2, 3, 4, 5, 0, 0, 0, 0]
Arrays.copyOf()
int[] copied = Arrays.copyOf(arr, 10); //10 the the length of the new array System.out.println(Arrays.toString(copied)); copied = Arrays.copyOf(arr, 3); System.out.println(Arrays.toString(copied));
Output:
[1, 2, 3, 4, 5, 0, 0, 0, 0, 0]
[1, 2, 3]
2. The Major Difference
The difference is that Arrays.copyOf does not only copy elements, it also creates a new array.System.arrayCopy copies into an existing array.
If we read the source code of Arrays.copyOf(), we can see that it uses System.arraycopy().
public static int[] copyOf(int[] original, int newLength) { int[] copy = new int[newLength]; System.arraycopy(original, 0, copy, 0, Math.min(original.length, newLength)); return copy; }
总结：
1.copyOf()的实现是用的是arrayCopy();
2.arrayCopy()需要目标数组，对两个数组的内容进行可能不完全的合并操作。
3.copyOf()在内部新建一个数组，调用arrayCopy()将original内容复制到copy中去，并且长度为newLength。返回copy;
System.arraycopy() or Arrays.copyOf()
原文：http://www.cnblogs.com/slowd/p/4575541.html