Please follow the code below,
Resource.java,
public class Resource {
public void first() {
Thread t = Thread.currentThread();
try {
System.out.println(t.getName() + " : is accessing the method 'first' ");
synchronized (this) {
for (int num = 1; num <= 10; num++) {
System.out.println(t.getName() + " : NUM : " + num);
Thread.sleep(500);
if (num == 5) {
this.wait();
}
}
this.notify();
}
} catch (Exception e) {
e.printStackTrace();
}
}
public void second() {
Thread t = Thread.currentThread();
try {
System.out.println(t.getName() + " : is accessing the method 'second' ");
synchronized (this) {
for (int num = 1; num <= 10; num++) {
System.out.println(t.getName() + " : X : " + num);
Thread.sleep(500);
if (num == 7) {
this.notify();
this.wait();
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
ReqThread.java as follows,
public class ReqThread extends Thread{
public ReqThread(String name,Resource res){
this.setName(name);
this.res = res;
}
private Resource res;
@Override
public void run(){
try{
if("ONE".equals(this.getName())){
res.first();
}else{
res.second();
}
}catch(Exception e){
e.printStackTrace();
}
}
}
And MainClass.java,
public class MainClass {
public static void main(String [] args){
Resource res = new Resource();
ReqThread t1 = new ReqThread("ONE", res);
ReqThread t2 = new ReqThread("TWO", res);
t1.start();
t2.start();
}
}
You can see from the above code, i am trying to learn on thread communication using wait and notify mechanism.
Here one the thread 'ONE' starts first starts, than an counter 5 waits and releases the lock, and than thread 'TWO' proceeds (which was already in the waiting state) and than its counter reaches 7 notifies and waits.
So my question is when thread 'TWO' do notify in method 'second', does is releases the lock ?
the output of the above code is
ONE : is accessing the method 'first'
ONE : NUM : 1
TWO : is accessing the method 'second'
ONE : NUM : 2
ONE : NUM : 3
ONE : NUM : 4
ONE : NUM : 5
TWO : X : 1
TWO : X : 2
TWO : X : 3
TWO : X : 4
TWO : X : 5
TWO : X : 6
TWO : X : 7
ONE : NUM : 6
ONE : NUM : 7
ONE : NUM : 8
ONE : NUM : 9
ONE : NUM : 10
TWO : X : 8
TWO : X : 9
TWO : X : 10
Now, if I do the code change in Resource.java in method 'second' as below
if (num == 7) {
this.notify();
//this.wait();
}
the output of the code is
ONE : is accessing the method 'first'
ONE : NUM : 1
TWO : is accessing the method 'second'
ONE : NUM : 2
ONE : NUM : 3
ONE : NUM : 4
ONE : NUM : 5
TWO : X : 1
TWO : X : 2
TWO : X : 3
TWO : X : 4
TWO : X : 5
TWO : X : 6
TWO : X : 7
TWO : X : 8
TWO : X : 9
TWO : X : 10
ONE : NUM : 6
ONE : NUM : 7
ONE : NUM : 8
ONE : NUM : 9
ONE : NUM : 10
From the second output you can see, even if thread 'TWO' does notify(), than too it doesn't waits and continues its printing numbers,
is this because even if thread 'TWO' does notify() but than too the code is still in synchronized block, and it still has the lock which is not yet released ?
