Proof of concept.

percentageCalculator.java

import java.util.Scanner;

public class percentageCalculator {
	public String xStr = "0";
	public String yStr = "0";

	public static void main(String[] args) {
		float x = 0;
		float y = 0;
		float z = 0;

		Scanner scanner = new Scanner(System.in);

		System.out.print("Enter a score: ");
		x = scanner.nextFloat();

		System.out.print("Enter the maximum score: ");
		y = scanner.nextFloat();

		z = (float) ((x / y) * 100);

		System.out.println("You got " + x + "/" + y + ", which is " + z + "%.");
	}
}

The floats did take me a long time, though...