Example of efficiency comparison analysis of Java two-dimensional array copy

1.for loop

public static void show1(int[][] array){
        for(int i = 0;i < array.length;i++){
            for(int j = 0;j < array[i].length;j++){
                System.out.print(array[i][j]+" ");
            }
            System.out.println();
        }
    }

2.clone()

/**
 * 使用数组本身的 clone() 方法
 *
 * @param sourceArr 源数组
 * @param destArr   目标数组
 */
public static void copy3(int[][] sourceArr, int[][] destArr) {
    for (int i = 0; i < sourceArr.length; i++) {
        destArr[i] = sourceArr[i].clone();
    }
}

3.Arrays.arraycopy

int[][] array = {{1,2,3},{4,5,6}};
        int[][] array2 = new int[2][3];
        for(int i = 0;i < array.length;i++){
            System.arraycopy(array[i], 0, array2[i],
                    0, array[i].length);

4. Speed ​​comparison

arraycopy source code, this method copies the fastest and has no return value.

@HotSpotIntrinsicCandidate
public static native void arraycopy(Object src,  int  srcPos,
                                    Object dest, int destPos,
                                    int length);

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