Wait notify mechanism with synchronization
In posts of thread in Java, I wrote four posts about this topic:
Part 1. Basic Thread in java. How to create them?In posts of thread in Java, I wrote four posts about this topic:
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
As
mentioned in previous post [Part 3: Java Thread], we never know when the shared
resource is set or not yet set. We cannot make forever loop to check the state
of that resource. One solution for this solution is to use wait/notify
mechanism in java. The way to do that is we use [object.wait()] to wait for
other threads set the data. In the threads setting the data, we call
[object.notify()] to notify all threads are waiting for resource wake up, and
doing necessary process. Look at example below to see how wait/notify works.
import java.util.LinkedList;
public class SynchronizeDemo {
public static void main(String[] args) {
LinkedList resources = new LinkedList();
PusherThread pt = new PusherThread(resources, 100);
pt.start();
PrinterThread print1 = new PrinterThread(resources, "Print1", 100);
PrinterThread print2 = new PrinterThread(resources, "Print2", 50);
print1.start();
print2.start();
System.out.println("All threads are started!!!!");
}
}
class PusherThread extends Thread {
private LinkedList rs;
public PusherThread(LinkedList rs, int no) {
this.noOfElement = no;
this.rs = rs;
}
private int noOfElement = 10;
public void run() {
for (int i = 0; i < noOfElement; i++) {
synchronized (rs) {
rs.add(i);
rs.notify();
try {
Thread.sleep(300);
} catch
(InterruptedException e) {
}
}
}
System.out.println(noOfElement + " numbers are added to
the list!");
}
}
class PrinterThread extends Thread {
private LinkedList rs;
public PrinterThread(LinkedList rs, String name, long sleepTime) {
this.rs = rs;
this.sleepTime = sleepTime;
this.threadName = name;
}
private boolean start = true;
private long sleepTime = 100;
public void stop(boolean val) {
this.start = val;
}
public void sleepIn(long val) {
this.sleepTime = val;
}
private String threadName;
public void nameMe(String val) {
this.threadName = val;
}
public void run() {
while (start) {
//
synchronize helps us only one value is removed
synchronized (rs) {
if (!rs.isEmpty()) {
int val = rs.remove();// remove a value
System.out.println("[" + threadName + "],
Removed :" + val);
}else{
System.out.println("No more
data, waiting....");
try {
rs.wait();
}
catch
(InterruptedException e) {
}
}
}
try {
Thread.sleep(sleepTime);
} catch
(InterruptedException e) {
}
}
}
}
