Combination Sum (Leetcode), Java

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//'main' method must be in a class 'Rextester'.
//Compiler version 1.8.0_111

import java.util.*;
import java.lang.*;

class Rextester
{  
    public List<List<Integer>> combinationSum(int[] candidates, int target){
        List<List<Integer>> out = new ArrayList<List<Integer>>();
        helper(out,new ArrayList<Integer>(),candidates,target,0);
        return out;
    }
    //[2,3,5,6,7] , 7
    public void helper(List<List<Integer>> list,List<Integer> tmplist,int[] candidates,int target,int index){
        if(target==0)
            list.add(new ArrayList<>(tmplist));
        if(target<0)
            return;
        for(int i=index;i<candidates.length;i++){
            tmplist.add(candidates[i]);
            helper(list,tmplist,candidates,target-candidates[i],i);
            tmplist.remove(tmplist.size()-1);
            
        }
    }
    public static void main(String args[])
    {
        System.out.println("Hello, World!");
        Rextester obj = new Rextester();
        List<List<Integer>> out = obj.combinationSum(new int[]{2,3,6,7},7);
        for(List<Integer> lst : out){

for(Integer i:lst){
                System.out.print(i+" ");
            }
            System.out.println("");
        }
    }
}

[ + ] Show input
Compilation time: 0.93 sec, absolute running time: 0.16 sec, cpu time: 0.14 sec, memory peak: 18 Mb, absolute service time: 1,1 sec