I have been facing this problem for many days, Please help me out. I am implementing producer-consumer example using thread synchronization. I have made some twist in this traditional program. Instead of using only one queue object, i have used two Queue objects. But program is not working.. (PS- I know i can make this program work by using only one object of queue, But what if i want to use two queue objects ?? )
class Queue {
static int value;
static boolean valueSet = false;
public static final Object obj;
static {
obj = new Object();
}
void push() {
synchronized(Queue.obj) {
while( Queue.valueSet ) {
try {
Thread.sleep(1000);
}catch(Exception e) {}
}
System.out.print("\n\n Push:- " + (++(Queue.value)));
Queue.valueSet = true;
return;
}
}
void pop() {
synchronized(Queue.obj) {
while(!(Queue.valueSet)) {
try {
Thread.sleep(1000);
}catch(Exception e) {}
}
System.out.print("\n\n Pop:- " + Queue.value);
Queue.valueSet = false;
return;
}
}
}
class Producer implements Runnable {
Queue Q;
Thread P;
Producer(Queue Q) {
this.Q = Q;
P = new Thread(this);
P.start();
}
public void run() {
while(true) {
Q.push();
}
}
}
class Consumer implements Runnable {
Queue Q;
Thread C;
Consumer(Queue Q) {
this.Q = Q;
C = new Thread(this);
C.start();
}
public void run() {
while(true) {
Q.pop();
}
}
}
public class TestQueue {
public static void main(String[] args) {
Queue Q1 = new Queue();
Queue Q2 = new Queue();
Object obj = new Object();
Producer p = new Producer(Q1);
Consumer c = new Consumer(Q2);
}
}
I got the answer. My misconception was wait,notify and notifyall methods are of thread class. So i was invoking them on thread object.
Solution is to just invoke wait and notify method on shared static object other than thread.
Answer:-
class Queue {
static int value;
static boolean valueSet = false;
public static final Object obj;
static {
obj = new Object();
}
void push() {
synchronized(Queue.obj) {
while( Queue.valueSet ) {
try {
Queue.obj.wait();
Thread.sleep(1000);
}catch(Exception e) {
e.printStackTrace();
}
}
System.out.print("\n\n Push:- " + (++(Queue.value)));
Queue.valueSet = true;
Queue.obj.notify();
}
}
void pop() {
synchronized(Queue.obj) {
while(!(Queue.valueSet)) {
try {
Queue.obj.wait();
Thread.sleep(1000);
}catch(Exception e) {
e.printStackTrace();
}
}
System.out.print("\n\n Pop:- " + Queue.value);
Queue.valueSet = false;
Queue.obj.notify();
}
}
}
class Producer implements Runnable {
Queue Q;
Thread P;
Producer(Queue Q) {
this.Q = Q;
P = new Thread(this);
P.start();
}
public void run() {
while(true) {
Q.push();
}
}
}
class Consumer implements Runnable {
Queue Q;
Thread C;
Consumer(Queue Q) {
this.Q = Q;
C = new Thread(this);
C.start();
}
public void run() {
while(true) {
Q.pop();
}
}
}
public class TestQueue {
public static void main(String[] args) {
Queue Q1 = new Queue();
Queue Q2 = new Queue();
Producer p = new Producer(Q1);
Consumer c = new Consumer(Q2);
}
}