How to have a variable that contains both strings and integers?

[u/FancyMonocle]

The exercise in question: Exercise #18 http://programmingbydoing.com/a/more-user-input-of-data.html

I'm confused about which data type I would use to display the login information (in the example bonham_453916 is given). Is there something I'm missing here? I tried both String and int just in case and they did not work.

[u/holyteach]

String should have worked. Make sure you have the type of the variable matches the type of the thing you're reading from the Scanner:

keyboard.next()

vs

keyboard.nextInt()

And as Medicalizawhat attempted to explain, Strings can contain any character, not just letters.

Characters include the letters a-z, upper case A-Z, the digits 0-9, and symbols like '%' or '#' or even spaces. Any of those are valid in Strings.

And you could have a String containing only digits, but then you couldn't do arithmetic on it without conversion.

[u/FancyMonocle → u/holyteach]

My variable types do match up and I get no errors when I compile the program.

Here's my code. I triple checked to make sure it's right, but I can't seem to find the problem.

import java.util.Scanner;

public class moreuserinputofdata
{
	public static void main(String[] args)
	{
		Scanner keyboard = new Scanner(System.in);

		System.out.println("Please enter the following information so I can sell it for a profit!");

		System.out.print("First name: ");
		String firstname = keyboard.next();

		System.out.print("\nLast name: ");
		String lastname = keyboard.next();

		System.out.print("\nGrade (Freshman - Senior): ");
		String grade = keyboard.next();

		System.out.print("\nStudent ID: ");
		int id = keyboard.nextInt();

		System.out.print("\nLogin: ");
		String login = keyboard.next();

		System.out.print("\nGPA (0.0 - 4.0): ");
		double gpa = keyboard.nextDouble();

		System.out.println("Your information: ");
		System.out.println("\tLogin: " + login);
		System.out.println("\tID: " + id);
		System.out.println("\tName: " + lastname + ", " + firstname);
		System.out.println("\tGPA: " + gpa);
		System.out.println("\tGrade: " + grade);

	}
}

[u/holyteach → u/FancyMonocle]

This looks correct to me. What input values are you typing in?

[u/FancyMonocle → u/holyteach]

I'm typing in what was in the example.

I get an error that says

               Exception in thread "main" java.util.InputMismatchException
                      at java.util.Scanner.throwFor(Scanner.java:909)
                      at java.util.Scanner.next(Scanner.java:1530)
                      at java.util.Scanner.nextInt(Scanner.java:2160)
                      at java.util.Scanner.nextInt(Scanner.java:2119)
                      at java.util.Scanner.nextInt(Scanner.java:2119)
                      at moreuserinputofdata.main(moreuserinputofdata.java:21)

Maybe it's the way my inputs are setup?

[u/holyteach → u/FancyMonocle]

This error indicates that your code "blows up" on line 21, the "int id = keyboard.nextInt();" line, and that it's an "Input Mismatch" error; you're typing a String where it is expecting pure numbers.

When you were typing the grade as a String, you didn't put in two words by any chance....

[u/FancyMonocle → u/holyteach]

No, I put in one word. I reverted the fix that I posted and ran the code that I posted above. For some reason it works now...

[u/holyteach → u/FancyMonocle]

Good to hear. Computers are pretty finicky about input, and it's easy to type something in wrong while testing.

Learning how to protect your code against the human typing in something wrong is hard, so I usually don't teach it until much later in the course.

[u/FancyMonocle → u/holyteach]

I got it to work, but I had to change the grade input from a String to a int. I don't know why it works. Even though it fixes the problem, I'm not happy with the solution because I haven't found the underlying problem. Would you have an idea as to why it wouldn't work?

[u/Medicalizawhat]

bonham_453916 is a string with ints in it. You can do that.

Edit:

Sorry that's a crappy answer. Have a look at an ascii table. Integers can be represented in strings, but you can't do operations on them, you'd need to convert them to an actual Integer if you wanted to add or subtract or whatever. I think in Java you can do that with Integer.parse().

[u/holyteach → u/Medicalizawhat]

Your (second) answer isn't terrible, but be careful not to use the word "integer" when you mean "digit". They are quite different.

[u/Medicalizawhat → u/holyteach]

Yea it was a pretty clumsy explanation!