数组元素内两元素相加等于目标值，返回数组下标

来自 作者reed分享
import java.util.Arrays;
import java.util.HashMap;

/**
 * @auto dh
 * @create 2020-03-29-12:40
 */
public class Test019 {
    public static int[] testArith() {
        int[] arr = {12, 14, 18, 20};
        HashMap<Integer, Integer> hashMap = new HashMap<>();
        int target = 32;

        for (int i = 0; i < arr.length; i++) {
            int value = target - arr[i];
            if (hashMap.containsKey(value)) {
                return new int[]{hashMap.get(value), i};
            }
            hashMap.put(arr[i], i);
        }

        return null;

    }

    public static void main(String[] args) {
        System.out.println(Arrays.toString(testArith()));
    }
}