java 如何在java中复制数组而不是引用？

how to make copy of array instead of reference in java?

提问by meteors

I want to make an exact copy of given array to some other array but such that even though I change the value of any in the new array it does not change the value in the original array. I tried the following code but after the third line both the array changes and attains the same value.

我想将给定数组的精确副本复制到某个其他数组，但是这样即使我更改了新数组中 any 的值，它也不会更改原始数组中的值。我尝试了以下代码，但在第三行之后，数组都发生了变化并获得了相同的值。

int [][]a = new int[][]{{1,2},{3,4},{5,6}};
int[][] b = a;
b[1][0] = 7;

instead of the second line I also tried

而不是第二行我也试过

int[][] b = (int[][])a.clone();

int [][] b = new int [3][2];
System.arraycopy(a,0,b,0,a.length);

int [][] b = Arrays.copyOf(a,a.length);

None of these helped. Please suggest me an appropriate method. I've tested this piece of code in eclipse scrapbook.

这些都没有帮助。请建议我一个合适的方法。我已经在 eclipse 剪贴簿中测试了这段代码。

回答by Louis Wasserman

You have to copy each row of the array; you can't copy the array as a whole. You may have heard this called deep copying.

您必须复制数组的每一行；你不能复制整个数组。您可能听说过这称为深度复制。

Accept that you will need an honest-to-goodness forloop.

接受你需要一个诚实到善良的for循环。

int[][] b = new int[3][];
for (int i = 0; i < 3; i++) {
  b[i] = Arrays.copyOf(a[i], a[i].length);
}

回答by Universitas

System.arraycopy() should work for you, but it doesn't copy as a whole, it copies "from a specified position to a specified position," according to the java documentation.

System.arraycopy() 应该适合你，但它不会作为一个整体复制，它复制“从指定位置到指定位置”，根据 java 文档。