I have written this code, an implement of blocking queue:
public class MyBlockingQueue extends Thread{
final private List <Integer> queue;
public MyBlockingQueue(){
queue = new LinkedList<Integer>();
}
public synchronized int size () {
return queue.size();
}
public synchronized void enqueue(int num)
throws InterruptedException {
this.queue.add(num);
System.out.println(getName()+" "+num+" added");
notify();
}
public synchronized int dequeue()
throws InterruptedException{
while(queue.size() == 0)
wait();
return this.queue.remove(0);
}
1.I have tried to make two threads and force them to add some number to the queue and then remove it. Unfortunatley, it seems like each thread has its own object. how can I change the code so both threads will handle the same object and add/remove to the same blocking queue synchronously?
2.Have I write the dequeue function correctly (so that when one thread removes the last number from the queue and the queue size is now zero, other threads will wait until the enqueue will notify them ) ?
this is my tester:
public class Main {
//checks the blocking queue
public static void main(String[] args) throws InterruptedException {
final MyBlockingQueue mine = new MyBlockingQueue();
Thread t1 = new Thread(){
public void run(){
try {
mine.enqueue((int)(Math.random()*1000));
System.out.println(getName()+"<- enter");
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
};
}
};
Thread t2 = new Thread(){
public void run(){
try {
mine.dequeue();
System.out.println(getName()+"<-remove");
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
Thread t3 = new Thread(){
public void run(){
try {
mine.dequeue();
System.out.println(getName()+"<-remove");
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
Thread t4 = new Thread(){
public void run(){
try {
mine.enqueue((int)(Math.random()*1000));
System.out.println(getName()+"<-enter");
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
Thread t5 = new Thread(){
public void run(){
try {
mine.dequeue();
System.out.println(getName()+"<-remove");
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
Thread t6 = new Thread(){
public void run(){
System.out.println("thread 6 of entering began, should release last thread of remove");
try {
mine.enqueue((int)(Math.random()*1000));
System.out.println(getName()+"<-enter");
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
Thread t7 = new Thread(){
public void run(){
try {
mine.dequeue();
System.out.println(getName()+"<-remove");
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
Thread t8 = new Thread(){
public void run(){
try {
mine.dequeue();
System.out.println(getName()+"<-remove");
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
Thread t9 = new Thread(){
public void run(){
try {
mine.dequeue();
System.out.println(getName()+"<-remove");
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
Thread t10 = new Thread(){
public void run(){
try {
mine.dequeue();
System.out.println(getName()+"<-remove");
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
Thread t11 = new Thread(){
public void run(){
System.out.println("thread 11 come to help, this comment before entering, after that we should see one add one remove");
try {
mine.enqueue((int)(Math.random()*1000));
System.out.println(getName()+"<-enter");
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
t1.start();
t2.start();
t3.start();
Thread.sleep(5000);
t4.start();//will the remove wai for the enter
Thread.sleep(5000);
/////4 tries to remove, one enter
t5.start(); //requesting to remove before have something
t7.start();
t8.start();
t9.start();
t10.start();
Thread.sleep(5000);
t6.start();
Thread.sleep(20000);//after 20 sec, t11 come to help
t11.start();
}
}
here is the output:
Thread-0 enqueued 1
Thread-1<- enter
Thread-0 dequeued 1
Thread-2<-remove
Thread-0 enqueued 4
Thread-0 dequeued 4
Thread-3<-remove
Thread-4<-enter
thread 6 of entering began, should release last thread of remove
Thread-0 enqueued 6
Thread-0 dequeued 6
Thread-5<-remove
Thread-6<-enter
thread 11 come to help, this comment before entering, after that we should see one add one remove
Thread-0 enqueued 11
Thread-0 dequeued 11
Thread-8<-remove
Thread-11<-enter
