SpecialStack.java

package Stack;

public class SpecialStack extends Stack<Integer> {
        Stack<Integer> min = new Stack<>();
      
        /* SpecialStack's member method to 
    insert an element to it. This method
        makes sure that the min stack is 
    also updated with appropriate minimum
        values */
        void push(int x)
        {
            if (isEmpty() == true) {
                super.push(x);
                min.push(x);
            }
            else {
                super.push(x);
                int y = min.pop();
                min.push(y);
                if (x < y)
                    min.push(x);
                else
                    min.push(y);
            }
        }
    public Integer pop()
    {
        int x = super.pop();
        min.pop();
        return x;
    }
  
    /* SpecialStack's member method to get 
minimum element from it. */
    int getMin()
    {
        int x = min.pop();
        min.push(x);
        return x;
    }
    public static void main(String[] args) {
        SpecialStack s = new SpecialStack();
        s.push(10);
        s.push(20);
        s.push(30);
        System.out.println(s.getMin());
        s.push(5);
        System.out.println(s.getMin());
    }
}