Question

Can anyone share simple sample of using Semaphore?
If it’s possible a sample of solving a task without semaphore and then with semaphore to understand main idea of it.

Answer 1

Here is a simple Semaphore implementation:

public class Semaphore {
  private boolean signal = false;

  public synchronized void take() {
    this.signal = true;
    this.notify();
  }

  public synchronized void release() throws InterruptedException{
    while(!this.signal) wait();
    this.signal = false;
  }

}

The take() method sends a signal which is stored internally in the Semaphore. The release() method waits for a signal. When received the signal flag is cleared again, and the release() method exited.

Read this article and take a look at this example