package threadbook.ch08;

import java.util.*;

public class EarlyNotifyFix extends Object {

private List list;

public EarlyNotifyFix() {

list = Collections.synchronizedList(new LinkedList());

}

public String removeItem() throws InterruptedException {

print("in removeItem() - entering");

synchronized ( list ) {

while ( list.isEmpty() ) {

print("in removeItem() - about to wait()");

list.wait();

print("in removeItem() - done with wait()");

}

// extract the new first item

String item = (String) list.remove(0);

print("in removeItem() - leaving");

return item;

}

}

public void addItem(String item) {

print("in addItem() - entering");

synchronized ( list ) {

// There'll always be room to add to this List

// because it expands as needed.

list.add(item);

print("in addItem() - just added: '" + item + "'");

// After adding, notify any and all waiting

// threads that the list has changed.

list.notifyAll();

print("in addItem() - just notified");

}

print("in addItem() - leaving");

}

private static void print(String msg) {

String name = Thread.currentThread().getName();

System.out.println(name + ": " + msg);

}

public static void main(String[] args) {

final EarlyNotifyFix enf = new EarlyNotifyFix();

Runnable runA = new Runnable() {

public void run() {

try {

String item = enf.removeItem();

print("in run() - returned: '" +

item + "'");

} catch ( InterruptedException ix ) {

print("interrupted!");

} catch ( Exception x ) {

print("threw an Exception!!!\n" + x);

}

}

};

Runnable runB = new Runnable() {

public void run() {

enf.addItem("Hello!");

}

};

try {

Thread threadA1 = new Thread(runA, "threadA1");

threadA1.start();

Thread.sleep(500);

// start a *second* thread trying to remove

Thread threadA2 = new Thread(runA, "threadA2");

threadA2.start();

Thread.sleep(500);

Thread threadB = new Thread(runB, "threadB");

threadB.start();

Thread.sleep(10000); // wait 10 seconds

threadA1.interrupt();

threadA2.interrupt();

} catch ( InterruptedException x ) {

// ignore

}

}

}