Using scanner input to make a for loop

Question

I am trying to make a sort of ATM. I want the program to do the following: If a user enters a number, the number gets multiplied by 12.

I already have the following code:

import java.util.Scanner;

public class DisplayMultiples {

    public static void main(String args[]) {


        Scanner keyboardInput = new Scanner(System.in);
        System.out.println("Enter a number between 1 and 12 ");
        keyboardInput.nextLine();  

        int b = 12;

        if() {
        for (int i = 1; i < b; i++) {

            System.out.println(i*b);


            }
        else {
             System.out.println("Error, this value is never used");
                }
        }
    }

"_this question may sound stupid._" I don't see where you asked any question. — takendarkk, Feb 11 '19 at 16:13
I indeed want to know what I have to write in the If/else statement. — Stijn van Woerkom, Feb 11 '19 at 16:19

score 1 · Accepted Answer · answered Feb 11 '19 at 16:13

1

Convert the input to a number.
If the input is not a number, show error message, and exit.
If the input is a number, multiply it by 12, show result, and exit.

answered Feb 11 '19 at 16:13

m0skit0

25,268
11
79
127

score 0 · Answer 2 · answered Feb 11 '19 at 16:15

The easiest way is to get an int from the Scanner and then check if it's between 1 and 12, and if so, multiply it by 12.

Scanner keyboardInput = new Scanner(System.in);
System.out.println("Enter a number between 1 and 12 ");
int number = keyboardInput.nextInt();
if (number > 0 && number < 13) {
    System.out.println(number * 12);
} else {
    System.out.println("Error, this value is never used");
}

Note that as you are likely a beginner, entering anything but an int in the console will result in an error but I assume that's not entirely necessary for you. If it is, read up on try...catch.

score -1 · Answer 3 · answered Feb 11 '19 at 16:30

-1

This way will avoid exceptions when entering non numbers.

    Scanner keyboardInput = new Scanner(System.in);
    System.out.println("Enter a number between 1 and 12 ");
    String inpStr = keyboardInput.nextLine();
    int b = 12;
    int inpVal = -1;

    try {
        inpVal = Integer.parseInt(inpStr);
    } catch (NumberFormatException nfe) {

    }

    if (inpVal >= 1 && inpVal <= 12) {
        System.out.println(inpVal * b);
    } else {
        System.out.println("Error, this value is never used");
    }

answered Feb 11 '19 at 16:30

Michael Besteck

2,415
18
10

2

Never ever have empty catch blocks – m0skit0 Feb 11 '19 at 16:35
@m0skit0 Why? Is that your private rule? The code compiles without error, and is working correctly. I expect an explanation. – Michael Besteck Feb 12 '19 at 15:36
https://stackoverflow.com/questions/1234343/why-are-empty-catch-blocks-a-bad-idea – m0skit0 Feb 12 '19 at 15:58
@m0skit0 Even your quote says "Occasionally this may be the right thing to do". Seems you did not analyse my answer. Any code in the catch block would be redundant, which would be a real bad thing. Your downvote seems not be based on logic and code understanding. – Michael Besteck Feb 19 '19 at 16:10

Using scanner input to make a for loop

3 Answers3