SortAStack.java

import java.util.*;
public class SortAStack {
    public static void sort(Stack<Integer> s){
        if (s.isEmpty()){
            return;
        }
        int top=s.pop();
        sort(s);
        insertAtCrtPos(s , top);
    }
    public static void insertAtCrtPos(Stack<Integer>s ,int top){
        if (s.isEmpty() || s.peek()<top){
            s.push(top);
            return;
        }
        int ele=s.pop();
        insertAtCrtPos(s , top);
        s.push(ele);
    }
    public static void main(String[] args) {
        Stack<Integer> s = new Stack<>();
        s.push(30);
        s.push(20);
        s.push(10);
        s.push(40);
        sort(s);
        while(!s.isEmpty()){
            System.out.println(s.peek());
            s.pop();
        }
    }
}