How to interrupt a read operation using BufferedReader (Java)?

Question

Hello although I read a lot of other answeres I do not understand how to close BufferedReader without sending input. This is the blocking part of my program:

public class AuctionClientUserListener extends Thread {

    private PrintWriter out;
    private BufferedReader stdIn;
    private int udpPort;
    private boolean running = true;
    private boolean listening = true;

    // needs server connection out
    public AuctionClientUserListener(BufferedReader stdIn,PrintWriter out,int udpPort) {
        this.stdIn = stdIn;
        this.out = out;
    }

    public void run() {
        String fromUser;

        while(true) {
            if(!listening) {
                break;
            }
            try {

                fromUser = stdIn.readLine(); // BLOCKS

                if (fromUser != null) {
                        System.out.println("Me: " + fromUser);

                        // check if to send udp port
                        String[] spinput = fromUser.split(" ");
                        if(spinput[0].equals("!login")) {
                            fromUser+=" "+udpPort;
                        }

                        out.println(fromUser);

                        if(fromUser.equals("!end")) {
                            listening = false;
                        }
                }
            } catch(Exception e) {
                listening = false;
            }
        }
        running = false;
    }

    public boolean running() {
        return running;
    }

    public void endListening() {

        this.listening =  false;
    }
}

When I call "endListening()" from the main thread, the program terminates - but NOT BEFORE the user inputs anything. I want to the program to terminate instantly - how to intterupt this BufferdReader (is created like BufferedReader(new InputStreamReader(System.in)) )?

I tried to call stdIn.close() and also thread.interrupt() on this Thread in the main Thread, but it ist not working. I also tried to close the InputStreamReader in the main Thread.

The people are being distracted by the title. I would advise a title like "Interrupt a read operation" or "Unblock a read operation". — SJuan76
– SJuan76, Commented Nov 23, 2012 at 14:59

durron597 · Accepted Answer · 2012-11-23 15:07:24Z

1

You could check to see if there's data available before calling BufferedReader.readLine(), i.e.

while(true) {
    if (!listening) break;
    if (System.in.available() > 0) {
        try {
            fromUser = stdIn.readLine();
            // etc.

edited Nov 23, 2012 at 15:07

answered Nov 23, 2012 at 14:56

durron597

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2 Comments

SJuan76 Over a year ago

If there is say, one character a in the inputsream, your check will pass but the readLine will still block waiting for the endline character.

Blackbam Over a year ago

Great, that solved the problem. Although I still wonder if there is another possibility.

SJuan76 · Accepted Answer · 2012-11-23 14:56:20Z

1

You must use thread.interrupt to signal the thread to interrupt its process. Be ready to catch an InterruptedException launched by the thread.

http://docs.oracle.com/javase/tutorial/essential/concurrency/interrupt.html

answered Nov 23, 2012 at 14:56

SJuan76

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Comments

Arunprasad · Accepted Answer · 2012-11-23 14:56:33Z

0

i think u can close your BufferedReader using stdIn.close();

answered Nov 23, 2012 at 14:56

Arunprasad

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