InterruptedException; must be caught or declared to be thrown

Question

I keep getting the following error:

 PrintServerV1.java:63: error: unreported exception InterruptedException; must be caught or declared to be thrown
        server.printRequest("homework7.txt");
                           ^
PrintServerV1.java:64: error: unreported exception InterruptedException; must be caught or declared to be thrown
        server.printRequest("assignment4.txt");
                           ^
PrintServerV1.java:65: error: unreported exception InterruptedException; must be caught or declared to be thrown
        server.printRequest("speech.pdf");

And I am pretty sure that I have thrown the error. This error only happens when add the following line: Thread.sleep(1000) Here is my code:

import java.util.*;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.locks.Condition;

import static java.lang.System.out;

public class PrintServerV1 implements Runnable {

    private static final Queue<String> requests = new LinkedList<String>();
    private Lock lock = new ReentrantLock();
    private Condition condition = lock.newCondition();

    public void printRequest(String s)  throws InterruptedException   {
        lock.lock();
        try {
            out.println("Adding print request for: " + s);
            requests.add(s);
            condition.signal();
        } finally { lock.unlock(); Thread.sleep(1000);}


    }

    public void sendRequest() throws InterruptedException {
        lock.lock();
        try {
            while (requests.size() == 0) {
                condition.await();
            }
            out.println("Sending Request to printer");
            Thread.sleep(1000);
            while (!requests.isEmpty()) {
                realPrint(requests.remove());
            }
        } finally {
            lock.unlock();
        }
    }

    private void realPrint(String s) throws InterruptedException  {
        // do the real work of outputting the string to the screen
        out.println("Currently printing: " + s);
        Thread.sleep(1000);
    }

    public void run() {
        try {
            sendRequest();
        } catch (InterruptedException exception) {}
    }

    public static void main(String[] args) {
        PrintServerV1 server = new PrintServerV1();
        new Thread(server).start();
        server.printRequest("homework7.txt");
        server.printRequest("assignment4.txt");
        server.printRequest("speech.pdf");
    }
}

Those are _compiler_ errors, not runtime errors. No exception has been thrown, as the program cannot actually be executed. It is telling you that your `printRequest` is declared to throw `InterruptedException` but you are not catching it in the code that calls `printRequest`. — Jim Garrison, Apr 22 '18 at 18:26
This is well explained in any introduction to exceptions tutorial. Please have a look at [this one](https://docs.oracle.com/javase/tutorial/essential/exceptions/) — Hovercraft Full Of Eels, Apr 22 '18 at 18:27

score 1 · Answer 1 · answered Apr 22 '18 at 18:32

Because your printRequest method throws an InterruptedException, it must be caught in main, or thrown by main... either one of the following answers ought to work ...

public static void main(String[] args) throws InterruptedException {
    PrintServerV1 server = new PrintServerV1();
    new Thread(server).start();
    server.printRequest("homework7.txt");       // these throw an exception
    server.printRequest("assignment4.txt");     // That is "InterruptedException"
    server.printRequest("speech.pdf");          // It must be caught, or declared thrown!
                                                // Version 1 declares it thrown (above in method declaration)
}


public static void main(String[] args) {
    PrintServerV1 server = new PrintServerV1();
    try {
        new Thread(server).start();
        server.printRequest("homework7.txt");
        server.printRequest("assignment4.txt");
        server.printRequest("speech.pdf");
    catch (InterruptedException e) { e.printStackTrace(); } // Version 2 catches it
}

InterruptedException; must be caught or declared to be thrown

1 Answers1