What's wrong with this code?

Question

I am trying to use Scanner to make my calculator, bot operation's input doesn't work.
https://code.sololearn.com/cDrqeu2O28kr/?ref=app

Answer 1

//One scanner object is enough. Others won't work for same stream.

import java.util.Scanner;
public class Program
{
public static void main(String[] args) {

System.out.println("Please input a");
Scanner a = new Scanner(System.in);
System.out.println(a.nextDouble());
System.out.println("Please input operation");
//Scanner op = new Scanner(System.in);
System.out.println(a.next());
System.out.println("Please input ");
//Scanner b = new Scanner(System.in);
System.out.println(a.nextDouble());
}
}

//hope it helps