In the series of Java thread, I have wrote four posts about this topic:
Part 1. Basic Thread in java. How to create them?
Part 2. Thread in java: method revisiting
Part 3. Thread in Java: Thread synchronization (or thread safe)
Part 4: Java thread synchronization and wait/notify mechanism
One case study is writing queue for sharing data between many threads. I have used this queue in many projects like web, restful which requires sharing data between many unknown threads.
/**
*
* @author LuyenCHU
*/
import
java.util.Collection;
import
java.util.LinkedList;
import
java.util.ListIterator;
import
java.util.logging.Level;
import
java.util.logging.Logger;
public class Queue {
private int maxQueueSize = 0;
private LinkedList queueData = new
LinkedList();
private boolean isWating = false;
public Queue() {
}
public Queue(int maxSize) {
maxQueueSize = maxSize;
}
public int size() {
synchronized (this) {
return queueData.size();
}
}
public boolean isEmpty() {
synchronized (this) {
return queueData.isEmpty();
}
}
public T dequeue() {
synchronized (this) {
T first = null;
if (size() > 0) {
first = queueData.removeFirst();
}
if (first == null) {
//will wait when no element in the
list
//System.out.println("No Data
found in the queue, waiting.......................");
isWating = true;
try {
this.wait();
} catch
(InterruptedException ex) {
Logger.getLogger(Queue.class.getName()).log(Level.SEVERE, null, ex);
}
}
return first;
}
}
public T dequeue(T obj) {
T found = null;
synchronized (this) {
found = find(obj);
if (found != null) {
queueData.remove(found);
}
}
return found;
}
public void enqueue(T obj) throws
IndexOutOfBoundsException {
//long
curr = System.currentTimeMillis();
//System.out.println("Added
one");
synchronized (this) {
if ((maxQueueSize > 0) && (size() >= maxQueueSize)) {
throw new
IndexOutOfBoundsException("Queue is full. Element not added.");
}
queueData.add(obj);
if (isWating) {
this.notify();
isWating = false;
}
}
//System.out.println("Add
Time : " + (System.currentTimeMillis() - curr));
}
public T find(T obj) {
synchronized (this) {
T current;
ListIterator iter = queueData.listIterator(0);
while (iter.hasNext()) {
current = iter.next();
if (current.equals(obj)) {
return current;
}
}
}
return null;
}
public void
addAll(Collection obj) {
synchronized (this) {
this.queueData.addAll(obj);
if (isWating) {
this.notify();
isWating = false;
}
}
}
}
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