java - 通过索引引用另一个数组

Question

是否可以通过 Java 中的索引以某种方式获取一个数组的引用，例如下面的伪代码:

array1 = [1,2,3,4,5,6,7,8] // size 8
array2 = [] // size 4
for(i=0 ; i<4 ; i ++)
{
  array2[i] = reference to array1[random(0,3)]
}

例如随机数是 3 0 4 6

array2[0] = array1[3]
array2[1] = array1[0]

如果将 array2[0] 更改为 99，则 array1[3]= 99 也会如此。

Answer 1

这并不完全可能，但你可以伪造它:

class Reference {

    private Object value;

    public Reference(Object value) {
        this.value = value;
    }

    public Object getValue() {
        return value;
    }

    public void setValue(Object value) {
        this.value = value;
    }

    @Override
    public String toString() {
        return value.toString();
    }

    public static Reference[] ofInts(int[] items) {
        Reference[] ret = new Reference[items.length];
        for(int i = 0; i < items.length; ++i) {
            ret[i] = new Reference(items[i]);
        }
        return ret;
    }
}

然后你可以像这样使用它:

int array1[] = new int[] {1,2,3,4,5,6,7,8};
Reference refArray1[] = Reference.ofInts(array1);

final int arr2Size = 4;
Reference refArray2[] = new Reference[arr2Size];
Random rand = new Random();

for(int i = 0; i < arr2Size; ++i) {
    int index = rand.nextInt(array1.length);
    refArray2[i] = refArray1[index];
}

System.out.println(Arrays.toString(refArray1));
System.out.println(Arrays.toString(refArray2));
System.out.println("---");

refArray2[0].setValue(99); // set reference value

System.out.println(Arrays.toString(refArray1));
System.out.println(Arrays.toString(refArray2));

示例输出:

[1, 2, 3, 4, 5, 6, 7, 8]
[4, 6, 3, 3]
---
[1, 2, 3, 99, 5, 6, 7, 8]
[99, 6, 3, 3]