https://leetcode.com/problems/two-sum java solution

SumTwo.java

import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

/**
 * @author richard.santana
 */
public class SumTwo {

	public static void main(String[] args) {
		Integer[] input = new Integer[]{11,2,7,15};
		Integer target = 9;
		System.out.println(Arrays.toString(verify(input, target)));
	}

	private static Integer[] verify(final Integer[] input,final Integer target) {
		Map<Integer, Integer> map = new HashMap<>();
		for(int i =0; i < input.length;i++){
			Integer value = map.get(input[i]);
			if(value != null){
				return new Integer[] {value,i};
			}else{
				Integer missing = target - input[i];
				map.put(missing,i);
			}
		}
		return null;
	}

}