Multithreading in Java
Last Updated :
24 Feb, 2021
Multithreading is a Java feature that allows concurrent execution of two or more parts of a program for maximum utilization of CPU. Each part of such program is called a thread. So, threads are light-weight processes within a process.
Threads can be created by using two mechanisms :
- Extending the Thread class
- Implementing the Runnable Interface
Thread creation by extending the Thread class
We create a class that extends the java.lang.Thread class. This class overrides the run() method available in the Thread class. A thread begins its life inside run() method. We create an object of our new class and call start() method to start the execution of a thread. Start() invokes the run() method on the Thread object.
Java
class MultithreadingDemo extends Thread {
public void run()
{
try {
System.out.println(
"Thread " + Thread.currentThread().getId()
+ " is running");
}
catch (Exception e) {
System.out.println("Exception is caught");
}
}
}
public class Multithread {
public static void main(String[] args)
{
int n = 8;
for (int i = 0; i < n; i++) {
MultithreadingDemo object
= new MultithreadingDemo();
object.start();
}
}
}
|
Output
Thread 15 is running
Thread 14 is running
Thread 16 is running
Thread 12 is running
Thread 11 is running
Thread 13 is running
Thread 18 is running
Thread 17 is running
Thread creation by implementing the Runnable Interface
We create a new class which implements java.lang.Runnable interface and override run() method. Then we instantiate a Thread object and call start() method on this object.
Java
class MultithreadingDemo implements Runnable {
public void run()
{
try {
System.out.println(
"Thread " + Thread.currentThread().getId()
+ " is running");
}
catch (Exception e) {
System.out.println("Exception is caught");
}
}
}
class Multithread {
public static void main(String[] args)
{
int n = 8;
for (int i = 0; i < n; i++) {
Thread object
= new Thread(new MultithreadingDemo());
object.start();
}
}
}
|
Output
Thread 13 is running
Thread 11 is running
Thread 12 is running
Thread 15 is running
Thread 14 is running
Thread 18 is running
Thread 17 is running
Thread 16 is running
Thread Class vs Runnable Interface
- If we extend the Thread class, our class cannot extend any other class because Java doesn’t support multiple inheritance. But, if we implement the Runnable interface, our class can still extend other base classes.
- We can achieve basic functionality of a thread by extending Thread class because it provides some inbuilt methods like yield(), interrupt() etc. that are not available in Runnable interface.
- Using runnable will give you an object that can be shared amongst multiple threads.
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