Java Do-While Loop is keeping the previous loop contents

Question

I'm doing this as a homework assignment for my first CS class, so I'm pretty new to Java. The goal is to create a program that checks a user input for a specified Java variable. There are three stipulations/outputs:

1. "Illegal" (no spaces allowed, must begin with a letter)
2. "Legal, but uses poor style" (should only use letters or digits)
3. "Good!"

If I run this program and type something like "variable" for the first loop, it will go through and print "Good!" by the end. And when the program asks again and I type something like "4variable", it will return "Illegal" - makes sense. The problem comes right after this. If I type the next variable like "variable" again, it will return "Illegal" because it still thinks there is a digit in the first character position. When I debug, it shows the "number" boolean set to 'true' even though it's false. I can't get it to drop the previous iteration of the loop.

Here is my code:

import java.util.Scanner;

public class IdentifierTestThree {

    public static void main(String[] args) {

        Scanner in = new Scanner(System.in);

        String userVariable = "";
        char ch = ' ';
        boolean space = false;
        boolean number = false;
        boolean capital = false;
        //boolean specialCharacter = false;
        boolean style = false;


        // State what this program does
        System.out.println("This program checks to see if a Java variable is legal or not.");

        // Get input from user
        System.out.println("Enter a variable: ");
        userVariable = in .nextLine();

        do {
            int variableParse = userVariable.length();
            for (int i = 0; i < variableParse; i++) {
                if ((Character.isLetterOrDigit(userVariable.charAt(i)) == false)) {
                    style = true;
                }
            }

            // Get the first character
            ch = userVariable.charAt(0);

            // Check each stipulation
            if (Character.isUpperCase(ch)) {
                capital = true;
            }
            if (Character.isDigit(ch)) {
                number = true;

            }
            if (userVariable.contains(" ")) {
                space = true;
            }

            if (space || number || capital) {
                System.out.println("Illegal");
            } else if (style) {
                System.out.println("Legal, but uses poor style.");
            } else {
                System.out.println("Good!");
            }

            // Ask the user to enter another variable or end the program
            System.out.println("Enter another variable or type 'Q' to quit.");
            userVariable = in .nextLine();

        } while (!userVariable.equalsIgnoreCase("Q"));

    }

}

Answer 1

You need to reset space, number, capital and style inside the do-loop which is processing a single variable. In fact you can move the declarations there as well, since the values are not needed outside that loop.

do { 
    boolean space = false;
    boolean number = false;
    boolean capital = false;
    //boolean specialCharacter = false;
    boolean style = false;

    int variableParse = userVariable.length();
    for (int i = 0; i < variableParse; i++) {
       if ((Character.isLetterOrDigit(userVariable.charAt(i)) == false)) {
           style = true;
       }
    }

    // Get the first character
    char ch = userVariable.charAt(0);


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