Java/Threads/CountDownLatch

An example of CountDownLatch.

  
   
import java.util.concurrent.CountDownLatch;
   
public class CDLDemo {
  public static void main(String args[]) {
    CountDownLatch cdl = new CountDownLatch(5);
    new MyThread(cdl);
   
    try {
      cdl.await();
    } catch (InterruptedException exc) {
      System.out.println(exc);
    }
    System.out.println("Done");
  }
}
   
class MyThread implements Runnable {
  CountDownLatch latch;
   
  MyThread(CountDownLatch c) {
    latch = c;
    new Thread(this).start();
  }
   
  public void run() {
    for(int i = 0; i<5; i++) {
      System.out.println(i);
      latch.countDown(); // decrement count
    }
  }
}

Count Up Down Latch

 
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 * modification, are permitted provided that the following conditions are met:
 *
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 *
 * Redistributions in binary form must reproduce the above copyright notice,
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 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL HSQL DEVELOPMENT GROUP, HSQLDB.ORG,
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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import java.util.concurrent.CountDownLatch;
public class CountUpDownLatch {
    CountDownLatch latch;
    int            count;
    public CountUpDownLatch() {
        latch      = new CountDownLatch(1);
        this.count = count;
    }
    public void await() throws InterruptedException {
        if (count == 0) {
            return;
        }
        latch.await();
    }
    public void countDown() {
        count--;
        if (count == 0) {
            latch.countDown();
        }
    }
    public long getCount() {
        return count;
    }
    public void countUp() {
        if (latch.getCount() == 0) {
            latch = new CountDownLatch(1);
        }
        count++;
    }
    public void setCount(int count) {
        if (count == 0) {
            if (latch.getCount() != 0) {
                latch.countDown();
            }
        } else if (latch.getCount() == 0) {
            latch = new CountDownLatch(1);
        }
        this.count = count;
    }
}