Thread: What's Wrong With My Code?

Whatever I input, it doesn't print out anything. All it keeps saying is to "Enter a variable name (q to quit): ". I'm pretty sure my coding is correct, I'm just having trouble putting it all together.

import java.util.Scanner;
 
public class Assign4 {
	public static void main(String[] args) {
		Scanner Input = new Scanner(System.in);
 
		String variableName;
		char ch;
		boolean legal = true;
 
		System.out.println("This program checks the properness of a proposed Java" +
			" variable name.");
		do {
			System.out.println("Enter a variable name (q to quit): ");
			variableName = Input.nextLine();
 
			if (variableName.isEmpty()) {
				System.out.println("Illegal.");
			}
			ch = variableName.charAt(0);
			if (!(Character.isUpperCase(ch))); {
				legal = false;
				System.out.println("Legal, but uses poor style.");
				}
			if ((!(Character.isDigit(ch)))) {
				legal = false;
				System.out.println("Illegal.");
			}
			else {
				System.out.println("Good.");
			}
			for (int i=1; i<variableName.length() && legal; i++) {
				ch = variableName.charAt(i);
				if(!(Character.isWhitespace(ch))) {
					legal = false;
				}
			}
			if (legal) {
				System.out.println("Good.");
			}
				}while(!Input.equals("q")); {
			System.out.println("End Program.");
	}
	}}

The program keeps asking for input. No errors. I will modify the program as you said and see if that helps. Thanks for responding snow.

Still is not outputting what it's supposed to. Here is my modified code.

import java.util.Scanner;
 
public class Assign4 {
	public static void main(String[] args) {
		Scanner Input = new Scanner(System.in);
 
		String variableName;
		char ch;
		boolean legal = true;
 
		System.out.println("This program checks the properness of a proposed Java" +
			" variable name.");
		do {
			System.out.println("Enter a variable name (q to quit): ");
			variableName = Input.nextLine();
 
			if (variableName.isEmpty()) {
				System.out.println("Illegal.");
			}
			ch = variableName.charAt(0);
			if else (!(Character.isUpperCase(ch))); {
				legal = false;
				System.out.println("Legal, but uses poor style.");
				}
			if else ((!(Character.isDigit(ch)))) {
				legal = false;
				System.out.println("Illegal.");
			}
			else {
				System.out.println("Good.");
			}
 
			for (int i=1; i<variableName.length() && legal; i++) {
				ch = variableName.charAt(i);
				if(!(Character.isWhitespace(ch))) {
					legal = false;
				}
			}
			if (legal) {
				System.out.println("Good.");
			}
				}while(!variableName.equals("q")); {
			System.out.println("End Program.");
 
	}
	}
	}

If I input q, it prints Good. Anything else and it just keeps repeating the first statement over and over again.

Originally Posted by snowguy13

The syntax of else if statements is else if(condition), not if else(condition).

Still doesn't output what I want it to. Do you think it has something to do with my Do loop? Modified code:

import java.util.Scanner;
 
public class Assign4 {
	public static void main(String[] args) {
		Scanner Input = new Scanner(System.in);
 
		String variableName;
		char ch;
		boolean legal = true;
 
		System.out.println("This program checks the properness of a proposed Java" +
			" variable name.");
		do {
			System.out.println("Enter a variable name (q to quit): ");
			variableName = Input.nextLine();
 
			if (variableName.isEmpty()) {
				System.out.println("Illegal.");
			}
			ch = variableName.charAt(0);
			else if (!(Character.isUpperCase(ch))); {
				legal = false;
				System.out.println("Legal, but uses poor style.");
				}
			else if ((!(Character.isDigit(ch)))) {
				legal = false;
				System.out.println("Illegal.");
			}
			else {
				System.out.println("Good.");
			}
 
			for (int i=1; i<variableName.length() && legal; i++) {
				ch = variableName.charAt(i);
				if(!(Character.isWhitespace(ch))) {
					legal = false;
				}
			}
			if (legal) {
				System.out.println("Good.");
			}
				}while(!variableName.equals("q")); {
			System.out.println("End Program.");
 
	}
	}
	}

Example: Input a variable name (q to quit):
if input is Bakercake it should output "legal, but uses poor style." because of capital first letter.
if input is baker cake2 it should output "illegal" because of space.
if input is 2baker it should output "illegal" because of digit first letter.
anything else for example, bakercake2, would be "good".
if input is q it should output "End Program"

Hi Nuggets!
I think your problem is that you pass a value to "ch" after the first if in your do while loop. I think it should go before the if statements.
And there is also a syntax error in the first else if statement:

else if (!(Character.isUpperCase(ch))); {
	legal = false;
	System.out.println("Legal, but uses poor style.");
}

Okay, so I rewrote my code again after my first failed attempt. What this program is supposed to do is to look for if a variable name that has been inputted is correct. If first character of variable name is a number, then it should print out "Illegal." If first character is capitalized, then it should print out "Legal." If there is a space, it should print out "Illegal." Also, if there is a '$' or '_' in the name, then it should print "Legal." Anything else that is inputted, for example "myName1", it should print out "Good." Entering "q" should print out "End Program." Here is my new code.

import java.util.Scanner;
 
public class Assign4 {
	public static void main(String[] args) {
		Scanner Input = new Scanner(System.in);
 
		String variableName;
		char ch;
		boolean legal = true;
		boolean proper = true;
 
		System.out.println("This program checks the properness of a proposed Java" +
			" variable name.");
		do {
			System.out.println("Enter a variable name (q to quit): ");
			variableName = Input.nextLine();
			ch = variableName.charAt(0);
			if (variableName.equalsIgnoreCase("q")) {
				System.out.println("End Program.");
 
			}
				else if (variableName.isEmpty()) {
					legal = false;
					proper = false;
 
				}
 
					if (Character.isUpperCase(ch)) {
						legal = false;
						proper = true;
					}
					else if (Character.isLetterOrDigit(ch) || ch == '$' || ch == '_') {
						legal = false;
						proper = false;
					}
 
			for (int i=1; i<variableName.length() && legal; i++) {
				ch = variableName.charAt(i);
 
				if (Character.isWhitespace(ch) || ch == '$' || ch == '_') {
					legal = false;
				}
			}
			if (legal) {
				System.out.println("Good.");
			}
			if (proper) {
				System.out.println("Legal, but uses poor style.");
			}
			else {
				System.out.println("Illegal.");
			}
				}while (variableName.equalsIgnoreCase("q")); {
			System.out.println("End Program.");
 
	}
	}
	}

What I'm having trouble on is when I input for example, "myName1", it prints "Illegal" when in fact it should print "Good." Also, if I input "q", then it will print out "End Program." and "Illegal." and the loop keeps going when it should end. All the other criteria's match and are fine. Any feedback would be nice.

Hey, This might help... your if statments are the problem. You seem to be checking for a false isUpperCase when what you want is a true.


if (Character.isUpperCase(ch)) {
legal = false;
System.out.println("Legal, but uses poor style.");
}

if (Character.isDigit(ch)) {
legal = false;
System.out.println("Illegal, The first character can't be a number.");
}

for (int i = 1; i < variableName.length() && legal; i++) {
ch = variableName.charAt(i);
if (Character.isWhitespace(ch)) {
legal = false;
}
}
if (legal) {
System.out.println("Good.");
}

} while (!variableName.equals("q"));
System.out.println("End Program.");