MinStack.java

import java.util.*;
public class MinStack{
    static Stack<Integer> stack=new Stack<>();
    static Stack<Integer> minStack= new Stack<>();
    public static void push(int val){
        stack.push(val);
        if (minStack.isEmpty() || minStack.peek()>=val){
            minStack.push(val);
        }
    }
    public static void pop(){
        if (stack.peek().equals(minStack.peek())){
            minStack.pop();
        }
        stack.pop();
    }
    public static int top(){
        return stack.peek();
    }
    public static int getMin(){
        return minStack.peek();
    }

    public static void main(String args[]){
        push(10);
        push(5);
        push(2);
        push(20);
        System.out.println("Top: " + top());
        System.out.println("Min: " + getMin());

        pop();

        System.out.println("Top after pop: " + top());
        System.out.println("Min after pop: " + getMin());
    }
}