Thread: Why won't this code loop?

Hello everyone, I'm brand new to java and also to this forum. Hoping to get some help and maybe help others when I get better at this.

Ok, so I tried to make a loop, if you enter "y" the code is supposed to loop, otherwise the program should terminate, but for some reason it won't loop, and I can't figure out what I'm doing wrong...

import java.util.Scanner;
 
public class scanner {
	public static void main (String args[]){
 
		Scanner scn = new Scanner(System.in);
		Scanner go = new Scanner(System.in);
 
		int fnum, snum, answer;
		String yn = "y";
 
		while(yn == "y"){	// this is there my loop starts
 
			System.out.print("enter first number: ");
			fnum = scn.nextInt();
			System.out.print("enter second number: ");
			snum = scn.nextInt();
			answer = fnum - snum;
			System.out.println(fnum + " - " + snum + " = " + answer);
 
			System.out.print("go again (y/n)? ");
			yn = go.nextLine();
			System.out.print(yn);	// just so make sure yn="y"
		}	
	}
}

Use the equals method to compare Strings, not the == operator.

Please post the code that created the error message.

It is this one, here without the ==.

The error message reads:

Exception in thread "main" java.lang.Error: Unresolved compilation problem:
Type mismatch: cannot convert from String to boolean

at scanner.main(scanner.java:12)

import java.util.Scanner;
 
public class scanner {
	public static void main (String args[]){
 
		Scanner scn = new Scanner(System.in);
		Scanner go = new Scanner(System.in);
 
		int fnum, snum, answer;
		String yn = "y";
 
		while(yn = "y"){	// this is there my loop starts
 
			System.out.print("enter first number: ");
			fnum = scn.nextInt();
			System.out.print("enter second number: ");
			snum = scn.nextInt();
			answer = fnum - snum;
			System.out.println(fnum + " - " + snum + " = " + answer);
 
			System.out.print("go again (y/n)? ");
			yn = go.nextLine();
			System.out.print(yn);	// just so make sure yn="y"
		}	
	}
}

while(yn = "y"){	// this is there my loop starts

The while statement requires a boolean value inside of the ().
Your code has an assignment statement inside of the ()s that evaluates to a String.

cannot convert from String to boolean

The compiler is complaining that there is no way to convert the String to the required boolean

Where are you using the equals() method that I recommended?