import java.util.Random;
import java.util.concurrent.Semaphore;
class Log{
public static void println(String s){
System.out.println(Thread.currentThread().getName() + " : " + s);
}
}
class BoundedResource{
private final Semaphore semaphore;
private final int permits;
private final static Random random = new Random(314159);
public BoundedResource(int permits){
this.semaphore = new Semaphore(permits);
this.permits = permits;
}
public void use() throws InterruptedException{
semaphore.acquire();
try{
doUse();
}
finally{
semaphore.release();
}
}
protected void doUse() throws InterruptedException{
Log.println("BEGIN : used = " + (permits - semaphore.availablePermits()));
Thread.sleep(random.nextInt(500));
Log.println("END : used = " + (permits - semaphore.availablePermits()));
}
}
class UserThread extends Thread{
private final static Random random = new Random(26535);
private final BoundedResource resource;
public UserThread(BoundedResource resource){
this.resource = resource;
}
public void run(){
try{
while(true){
resource.use();
Thread.sleep(random.nextInt(3000));
}
}
catch(InterruptedException e){
}
}
}
public class Main{
public static void main(String [] args){
BoundedResource resource = new BoundedResource(3);
for(int i = 0; i < 10; i++){
new UserThread(resource).start();
}
}
};
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