Re: Help in Threading when program waits for an input

Tom Hawtin <>
Tue, 29 May 2007 20:40:45 +0100
Mithil wrote:

I am using the following line to get input from the user in the
command prompt.

BufferedReader dis = new BufferedReader(new

The program does nothing until the user enter a value into it, is it
possible to use threads and do more work while waiting for the input.
If so how can I do it any code examples would be great :)

Threading is difficult.

For this example, assuming you just want to read lines of input and poll
for results:

     final BlockingQueue<String> input =
        new java.util.concurrent.ArrayBlockingQueue<String>(10);
     Thread thread = new Thread(new Runnable() {
             public void run() {
                 try {
                     BufferedReader in = new BufferedReader(
                         new InputStreamReader(
                     for (;;) {
                         String line = in.readLine();
                         if (line == null) {
                 } catch ( exc) {
                     // Oops... (perhaps should quit)
                     throw new Error(exc);
                 } finally {
             private void put(String line) {
                 for (;;) {
                     try {
                     } catch (java.lang.InterruptedException exc) {
                         // Ignore - we should keep going.
                         // IO may throw, however.

     outerLp: for (;;) {
         while (!input.isEmpty()) {
             String line = input.remove();
             if (line == null) {
                 // End of input.
                 break outerLp; // say
             ... do stuff with line ...
         ... do a little stuff while waiting ...

(Disclaimer: Not tested or even compiled.)

Tom hawtin

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