asked on

What is the code doing exactly and what is the theoretical reason why this code is not compiling? (part 1)

Please see below some java code which I am trying to compile and run. I am fully aware that the code has an error. I also know how to fix it (as you can see from the comment just below). What I don't however know is what this code is actually doing.
Is it looping infinitely? Does it stop abruptly? What is the exact reason behind why I get a compile error?

import java.util.Random;

public class PartA {

    //loop 10 times
    private static void loop2() {
        for(;;) System.out.println("In loop");
        //for(int i = 0; i < 10; i++) System.out.println("In loop");
        System.out.println("Out of loop");
    }

        private static void runLoops() {
		loop2();
		System.out.println();
	}


	public static void main(String[] args) {
		runLoops();
	}

}

Open in new window

thanks in advance

ASKER CERTIFIED SOLUTION

David Johnson, CD

membership

This solution is only available to members.

To access this solution, you must be a member of Experts Exchange.

Start Free Trial

CEHJ

What is the exact reason behind why I get a compile error?

Because the line the compiler will indicate is not reachable because it is preceded by an infinite loop

badwolfff

ASKER

When there are infinite loops the java compiler tells me "code taking more than 5 seconds to execute" and it kills it (compilejava.net).
Here I get a different error: Unable to execute program; could not compile!
/tmp/java_kmr4s7/PartA.java:9: error: unreachable statement
System.out.println("Out of loop");
^
1 error

So is this an infinite loop or something else? And if it is an infinite loop, why? What is the stop condition that is not being met?
thanks

CEHJ

You're really just repeating the question, but:

When there are infinite loops the java compiler tells me "code taking more than 5 seconds to execute" and it kills it (compilejava.net).

I'm not sure why you're using compilejava.net but it isn't helping you. Why? Because you're not able to distinguish between compilation and execution, which you would be able to do if you were using standard tools (javac+java). If something is able to be killed, it must be running, which means it must have been able to be, and was, compiled.

The differences you're seeing are due to cases where the compiler knows a loop won't ever finish, such that the next statement is unreachable and cases where it doesn't know, but the loop turns out to be infinite anyway

badwolfff

ASKER

Thanks. Got it.

CEHJ

Why did you accept only ONE answer, which evidently didn't answer your subsidiary questions?

badwolfff

ASKER

Ah I didn't realize that is how it is done in experts exchange. Sorry. Will keep it in mind next time unless I can change this selection.