PairSums.java

import java.util.*;
 
class Main
{
    public static void sumsTo(int nums[], int sum)
    {
        HashMap<Integer, Integer> hash = new HashMap<Integer, Integer>();
        for(int num : nums)
            hash.put(num, 1);
        
        for(int x = 0; x < nums.length; x++)
        {
            int y = sum - nums[x];
            
            if (hash.containsKey(y))
                System.out.println(nums[x] + " + " + y + " = " + sum);
        }
    }
    
    public static void main(String args[])
    {
        sumsTo(new int[] { 1,2,3,4,5 }, 6 );
    }
}