Java找出不重复无序数组中和为n的两数的下标

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

public class Demo5 {

    public static void main(String[] args) {

        int[] arr = new int[]{3, 4, 5, 9, 8};
        int num = 8;
        int[] ret = getIndex(arr, num);
        System.out.println("index of two number:" + ret[0]+" " + ret[1]);

    }

    //找到这两个数的下标，并以长度为2的数组形式返回
    public static int[] getIndex(int[] arr, int num){
        
        int[] ret = new int[2];   //长度为2的数组
        HashMap<Integer, Integer> hashMap = new HashMap<>();
        int index = 0;
        
        //将每个数字及其下标放入map中
        for (int i : arr) {
            hashMap.put(i, index++ );
        }

        //遍历 HashMap 并判断
        Iterator iterator = hashMap.entrySet().iterator();
        while (iterator.hasNext()){
            Map.Entry entry = (Map.Entry)iterator.next();

            int value = (int) entry.getKey();
            int subValue = num - value;

            if (hashMap.containsKey(subValue)){
                //找到了
                ret[0] = (int) entry.getValue();
                ret[1] = hashMap.get(subValue);
                break;
            }
        }
        return ret;

    }
}