Breaking out of an infinite loop after a user inputs a character-CodePudding

I want to make an infinite loop of a message and stops it if a user inputs a character for example "x". But its getting an error on the if statement saying that it is an unreachable code. Can someone help me.

import java.util.Scanner;
public class Loop {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        char y;

        while (true) {
            System.out.println("Good Morning!!!");
        }
        y = input.next().charAt(0);
        if (y == 'y') {
            break;
        }
    }   
}

CodePudding user response：

Your if statement is not inside the while loop:

import java.util.Scanner;
public class Loop {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        char y;

        while (true) {
            System.out.println("Good Morning!!!");
            y = input.next().charAt(0);
            if (y == 'y') {
                break;
            }
        }
    }   
}

CodePudding user response：

Acknowledgement

A thread is a thread of execution in a program. The Java Virtual Machine allows an application to have multiple threads of execution running concurrently. Every thread has a priority. Threads with higher priority are executed in preference to threads with lower priority. Each thread may or may not also be marked as a daemon. When code running in some thread creates a new Thread object, the new thread has its priority initially set equal to the priority of the creating thread, and is a daemon thread if and only if the creating thread is a daemon.

When a Java Virtual Machine starts up, there is usually a single non-daemon thread (which typically calls the method named main of some designated class). Read more about threads here

Solutions

Because both input & loop blocks the thread, you have to put them in seperate thread. Just like this :-

public class Demo {
    volatile static char input;

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

        new Thread(new Runnable() {
            @Override
            public void run() {
                while (input != 'y'){
                    System.out.println("Good morning !");
                }
            }
        }).start();

        input = scanner.next().charAt(0);
    }
}

This will print "Good morning !" until the input != 'y'. On the other hand, we are reading the input from user. As user enteres 'y', the condition get false and loop stops.

CodePudding user response：

Try this.

public static void main(String[] args) throws IOException {
    InputStream input = System.in;
    while (true) {
        System.out.println("Good Morning!!!");
        if (input.available() > 0 && input.read() == 'y')
            break;
    }
}