1.System.arraycopy
底层提供的方法，所以该方法native修饰
/*
*
* @param src the source array. 复制对象
* @param srcPos starting position in the source array. 复制数据起始位置
* @param dest the destination array. 目标数组
* @param destPos starting position in the destination data. 目标数组起始位置
* @param length the number of array elements to be copied. 复制个数
* @exception IndexOutOfBoundsException if copying would cause
* access of data outside array bounds.
* @exception ArrayStoreException if an element in the <code>src</code>
* array could not be stored into the <code>dest</code> array
* because of a type mismatch.
* @exception NullPointerException if either <code>src</code> or
* <code>dest</code> is <code>null</code>.
*/
public static native void arraycopy(Object src, int srcPos,
Object dest, int destPos,
int length);
2.简单实现数组复制
public static void main(String[] args) {
Integer[] a = new Integer[]{1, 2, 3, 4};
Integer[] a1 = new Integer[3];
//从a下标1开始复制3个
System.arraycopy(a, 1, a1, 0, a1.length);
System.out.println(Arrays.asList(a1));
}
输出结果
[2, 3, 4]
3.删除指定数组下标的元素
public static void main(String[] args) {
// Integer[] a = new Integer[]{1, 2, 3, 4};
// Integer[] a1 = new Integer[3];
// //从a下标1开始复制3个
// System.arraycopy(a, 1, a1, 0, a1.length);
// System.out.println(Arrays.asList(a1));
Integer[] a = new Integer[]{1, 2, 3, 4};
// System.arraycopy(a, 1, 1, 1, a.length - 1);
// a[a.length - 1] = null;
deleteIndex(a, 0);
System.out.println(Arrays.asList(a));
}
public static void deleteIndex(Integer[] arr, int index) {
int number = arr.length - 1 - index;
System.arraycopy(arr, index+1, arr, index , number);
System.out.println(Arrays.asList(arr));
arr[arr.length - 1] = null;
}
输出结果：
[2, 3, 4, 4]
[2, 3, 4, null]
