In this post we'll see a Java program to print odd and even numbers sequentially using two threads. One thread generates odd numbers and another even numbers. This Java program makes use of inter-thread communication using wait, notify, notifyAll to print odd-even numbers.
- Refer Print odd-even numbers using threads and semaphore to see how to print odd-even numbers using threads and semaphore.
Java program to print odd-even numbers using threads
There is a class SharedPrinter whose object is shared between two threads. In this class there is a method printEvenNum() for printing even numbers and method printOddNum() for printing odd numbers.
These two methods are called by the respective threads EvenNumProducer and OddNumProducer and these threads communicate using wait and notify, of course from inside a synchronized block.
- Refer Why wait(), notify() and notifyAll() must be called inside a synchronized method or block to know more about the topic.
public class EvenOddThreadDemo {
public static void main(String[] args) {
// shared class object
SharedPrinter sp = new SharedPrinter();
// creating two threads
Thread t1 = new Thread(new EvenNumProducer(sp, 10));
Thread t2 = new Thread(new OddNumProducer(sp, 10));
// starting threads
t1.start();
t2.start();
}
}
// Shared class used by both threads
class SharedPrinter{
boolean evenFlag = false;
//Method for printing even numbers
public void printEvenNum(int num){
synchronized (this) {
// While condition as mandated to avoid spurious wakeup
while(!evenFlag){
try {
//asking current thread to give up lock
wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
System.out.println(num);
evenFlag = false;
// Wake up thread waiting on this monitor(lock)
notify();
}
}
//Method for printing odd numbers
public void printOddNum(int num){
synchronized (this) {
// While condition as mandated to avoid spurious wakeup
while(evenFlag){
try {
//asking current thread to give up lock
wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
System.out.println(num);
evenFlag = true;
// Wake up thread waiting on this monitor(lock)
notify();
}
}
}
// Thread Class generating Even numbers
class EvenNumProducer implements Runnable{
SharedPrinter sp;
int index;
EvenNumProducer(SharedPrinter sp, int index){
this.sp = sp;
this.index = index;
}
@Override
public void run() {
for(int i = 2; i <= index; i = i+2){
sp.printEvenNum(i);
}
}
}
//Thread Class generating Odd numbers
class OddNumProducer implements Runnable{
SharedPrinter sp;
int index;
OddNumProducer(SharedPrinter sp, int index){
this.sp = sp;
this.index = index;
}
@Override
public void run() {
for(int i = 1; i <= index; i = i+2){
sp.printOddNum(i);
}
}
}
Output
1 2 3 4 5 6 7 8 9 10
That's all for this topic Print Odd-Even Numbers Using Threads And wait-notify Java Program. If you have any doubt or any suggestions to make please drop a comment. Thanks!
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