Java System.arraycopy 针对同一数组和两个数组

public class TestSystemArrayCopy {
public static void main(String[] args) {
//定义数组
int [] arr1 = new int[20];

//初始化数组
for (int i = 0 ;i < 20; i++) {
arr1[i] = i;
}

//show array
for (int i: arr1) {
System.out.print(i+ " ");
}
System.out.println();

//同一数组的 copy
System.arraycopy(arr1, 6, arr1, 2, 10);
for (int i: arr1) {
System.out.print(i+ " ");
}
System.out.println();
}
}
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
0 1 6 7 8 9 10 11 12 13 14 15 12 13 14 15 16 17 18 19

测试结果:对于同一个数组的拷贝System.arraycopy(arr, a, arr, b, c)(a, b , c 为arr 的合法下标)

结果为:arr[b] ~ arr[b + c -1] 替换为 arr[a] ~ arr[a + c - 1]

将数组 arr 中 下标从 b 开始的(包括arr[b])的c个元素 替换为从a开始(包括arr[a])的c个元素

移除数组某一下标的的值：

public class TestSystemArrayCopy {
public static void main(String[] args) {
//定义数组
int [] arr1 = new int[20];

//初始化数组
for (int i = 0 ;i < 10; i++) {
arr1[i] = i;
}

//show array
for (int i: arr1) {
System.out.print(i+ " ");
}
System.out.println();

//移除下标为6的值
System.arraycopy(arr1, 6 + 1, arr1, 6, 10);
for (int i: arr1) {
System.out.print(i+ " ");
}
System.out.println();
}
}
0 1 2 3 4 5 6 7 8 9 0 0 0 0 0 0 0 0 0 0
0 1 2 3 4 5 7 8 9 0 0 0 0 0 0 0 0 0 0 0



两个数组的拷贝:
public class TestSystemArrayCopy {
public static void main(String[] args) {
//定义数组
int [] arr1 = new int[20];
int [] arr2 = new int[20];

//初始化数组
for (int i = 0 ;i < 20; i++) {
arr1[i] = i;
arr2[i] = 2 * i;
}

//show array
for (int i: arr1) {
System.out.print(i+ " ");
}
System.out.println();

for (int i: arr2) {
System.out.print(i+ " ");
}
System.out.println();

//数组copy
System.arraycopy(arr1, 5, arr2, 2, 10);
for (int i: arr1) {
System.out.print(i+ " ");
}
System.out.println();
for (int i: arr2) {
System.out.print(i+ " ");
}
System.out.println();
}
}
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
0 2 5 6 7 8 9 10 11 12 13 14 24 26 28 30 32 34 36 38

测试结果:System.arraycopy(arr1, a, arr2, b, c)

                 arr1 不变 
                 arr2: arr2[b] ~ arr2[b + c -1] 替换为 arr1[a] ~ arr1[a + c - 1]

将数组 arr2 中 下标从 b 开始的(包括arr2[b])的c个元素 替换为从arr1 中 a开始(包括arr1[a])的c个元素