Nearest Greater to right | Next Largest Element

package org.ms.ds.stack;

import java.util.*;

/*
Identify : if we have nested loop and i depends on j then think of stack
Example : input array [1,3,2,4] => output [3,4,4,-1]
Algorithm: using stack
1. take one temporary list and stack
2. traverse given stack from end of list
3(a). if stack is empty push add -1 in list
3(b). if stack is not empty
           if stack top element is greater than source list element
                copy stack top in temp list
           else
                keep popping element from stack until find greater and add in temp list and if not found then add -1 in temp list
4. push new element in stack
5. return temp list after reverse
 */
public class NearestGreaterToRight {

    List<Integer> getNGR(List<Integer> eles){
        List<Integer> temp=new ArrayList<>();
        Stack<Integer> stack=new Stack<>();
        for(int item=eles.size()-1;item>=0;item--){
           if(stack.empty()){
               temp.add(-1);
           }else if(stack.size() > 0 && stack.peek() > eles.get(item)){
               temp.add(stack.peek());
           }else if(stack.size() > 0 && stack.peek() <= eles.get(item)){
               while(stack.size() > 0 && stack.peek() <= eles.get(item)){
                   stack.pop();
               }
               if(stack.size() ==0){
                   temp.add(-1);
               }else{
                   temp.add(stack.peek());
               }
            }
           stack.push(eles.get(item));
        }
        Collections.reverse(temp);
        return temp;

    }

    public static void main(String[] args) {
      NearestGreaterToRight nearestGreaterToRight=new NearestGreaterToRight();
      List<Integer> sl=new ArrayList<>();
      sl.add(1);
      sl.add(3);
      sl.add(2);
      sl.add(4);
      System.out.println(nearestGreaterToRight.getNGR(sl));
    }
}