Else on if statement is not going through

Question

So I'm a noob coder (new to the website), trying to teach myself and I'm currently making a simple calculator. Atm, I've added pi to it with an if statement that checks the input. However, when I type a double it doesn't do anything and I'm not sure why.

package testing;
import java.util.Scanner;

public class Calculator {


@SuppressWarnings("resource")
public static void main(String[] args) {
    String piCheck = "pi";
    Double n1 = null;

    Scanner reader = new Scanner(System.in);

    System.out.println("Welcome to Calculator!");
    System.out.println(" ");

    System.out.println("Enter a number, ");
    System.out.println("or enter 'pi' to insert PI,");
    if (reader.nextLine().toLowerCase().contains(piCheck)) {
        n1 = Math.PI;
    } else {
        n1 = reader.nextDouble();
    }

    Scanner reader2 = new Scanner(System.in);
    System.out.println("Would you like to multiply, divide, add, subtract?");
    String uOperation = reader2.nextLine();


    int operation = 1;
    switch (uOperation.toLowerCase()) {
        case "multiply":
            operation = 1;
            break;

        case "multiplication":
            operation = 1;
            break;

        case "times":
            operation = 1;
            break;

        case "divide":
            operation = 2;
            break;

        case "division":
            operation = 2;
            break;

        case "add":
            operation = 3;
            break;

        case "addition":
            operation = 3;
            break;

        case "subtract":
            operation = 4;
            break;

        case "subtraction":
            operation = 4;
            break;

        default:
            System.out.println("Invalid operation! Rerun Calculator!");
            break;

    }


    if (operation == 1) {

        System.out.println("What do you want to multiply " + n1 + " by?");

    } else if (operation == 2) {

        System.out.println("What do you want to divide " + n1 + " by?");

    } else if (operation == 3) {

        System.out.println("What do you want to add to " + n1 + "?");

    } else if (operation == 4) {

        System.out.println("What do you want to subtract from " + n1 + "?");

    } else {
        System.out.println("Something went wrong!");
    }
    double n2 = reader.nextDouble();


    System.out.println("Here's your result!");
    double resultM = n1*n2;
    double resultD = n1/n2;
    double resultA = n1+n2;
    double resultS = n1-n2;

    if (operation == 1) {

        System.out.println(n1 + " multiplied by " + n2 + " equals:");
        System.out.println(resultM);

    } else if (operation == 2) {

        System.out.println(n1 + " divided by " + n2 + " equals:");
        System.out.println(resultD);

    } else if (operation == 3) {

        System.out.println(n1 + " plus " + n2 + " equals:");
        System.out.println(resultA);

    } else if (operation == 4) {

        System.out.println(n1 + " take away " + n2 + " equals:");
        System.out.println(resultS);

    } else {
        System.out.println("Something went wrong!");
    }
}

}

Answer 1

Your problem is that you are reading the input in the condition, so if you enter a double, the else clause expects more input to be entered, since the first input was already consumed by reader.nextLine().

You have to save the input and reuse it :

String input = reader.nextLine();
if (input.toLowerCase().contains(piCheck)) {
    n1 = Math.PI;
} else {
    n1 = Double.parseDouble(input);
}