How to use boolean to add numbers input by user?

Question

I am writing this program for school work that asks the user to input a sequence of letters and numbers and determine whether it is a digit or not.

My teacher wants me to add up the characters that are digits(numbers) and output it as "Your numbers added up together are: place added number here" and output the letters are a string saying "These are your letters: *place letters here."

I think I got the code right that determines whether it is a digit or not but how do I end up adding them? I tried using an if statement that checked if Character.isDigit is true but I keep getting errors and I think I'm writing it totally wrong. Any response would be greatly appreciated.

Here is my code:

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

    int sum1 = 0;
    String stringFull = "";
    boolean isTrue = Character.isDigit(string1.charAt(i));




    Scanner getString = new Scanner(System.in);
    System.out.println("Please enter a sequence of letters: ");
    String string1 = getString.nextLine();

    for(int i = 0; i < 5; i++)
    {
        if (Character.isDigit(string1.charAt(i)))
        {
            sum1 += Character.getNumericValue(string1.charAt(i));

        } else {
            stringFull += string1.charAt(i);
        }

        if (isTrue)
        {
             System.out.println(sum1 * sum1);
        }

    }




}

}

In Java you can't use variables that you haven't yet declared. For instance, when you try boolean isTrue = Character.isDigit(string1.charAt(i));, i doesn't exist yet. — azurefrog
– azurefrog, Commented Jan 26, 2018 at 17:30

Ravi · Accepted Answer · 2018-01-26 17:43:01Z

1

You will get compilation error for below as i wasn't declared before this line

boolean isTrue = Character.isDigit(string1.charAt(i));

instead you should initialize it with false

boolean isTrue = false;

Then, your loop should loop till given string length, but you have hard-coded to 5, which will cause exception at runtime when string length is less than 5.

 for(int i = 0; i < 5; i++)

should change to

 for(int i = 0; i < string1.length(); i++)

Also, inside you for loop you are have following line of code, but you have never changed isTrue value inside the loop.

if (isTrue)
{
    System.out.println(sum1 * sum1);
}

And, I think, right place to change isTrue value, where you are checking for digit.

if (Character.isDigit(string1.charAt(i)))
{
    sum1 += Character.getNumericValue(string1.charAt(i));
    isTrue = true;
}

edited Jan 26, 2018 at 17:43

answered Jan 26, 2018 at 17:34

Ravi

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Comments

Joan Amoros · Accepted Answer · 2018-01-26 17:41:36Z

0

You should use

Integer.parseInt(String.valueOf(string1.charAt(i)))

which returns the number, instead of

Character.getNumericValue(string1.charAt(i))

which returns the ascii code for the number

answered Jan 26, 2018 at 17:41

Joan Amoros

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