Thread is a path of independent execution in a program.
Well, this line doesn’t seem to be much clear. We will understand it better by relating it to the concept of the operating system.
We have a processor in our CPU which is responsible for the execution of all the programs. But, there are many programs that want to be executed by a single processor, while a processor can work on only a single program at a time. To handle this problem, all the processes are connected via a thread to the processor. Then, the processor executes a thread for a limited amount of time, and after some time, it jumps to the next process. This concept is also called scheduling. Due to this, an illusion is created that the processor is simultaneously executing all the tasks, which is actually not possible for a processor to do. It will run only a single program at a time, and the altering is so fast that it seems as if all the tasks are processing at the same time.
Similar things happen in the case of a single Java program. Multiple pieces of code are connected via threads, and these pieces of code execute simultaneously in a time-sharing manner. This is called the concept of threading.
Every thread in Java is created and controlled by a class named java.lang.Thread
How to create a Thread in Java
There are two ways to create a thread in java –
- Implement the Runnable interface(java.lang.Runnable)
- By Extending the Thread class(java.lang.Thread)
Implementing Thread using Runnable class –
It is the easiest way to create a thread by implementing Runnable. One can create a thread on any object by implementing Runnable. To implement a Runnable, one has only to implement the run method.
public void run()
We will understand this better with the help of the example given below-
public void run(){
int i;
for(int i=0;i<=10;i++){System.out.println(“Thread A” +i);}
}
Class B implements Runnable{
public void run(){
int i;
for(int i=0;i<=10;i++){System.out.println(“Thread B” +i);}
}
}
public class Example{
public static void main(String[] args){
Thread t1= new Thread(new A());
Thread t2 = new Thread(new B());
t1.start();
t2.start();
}
}
Output –
Thread B 0 Thread B 1 Thread A 0 Thread B 2 Thread A 1 Thread B 3 Thread A 2 Thread B 4 Thread A 3 Thread B 5 Thread A 4 Thread B 6 Thread A 5 Thread B 7 Thread A 6 Thread B 8 Thread A 7 Thread B 9 Thread A 8 Thread B 10 Thread A 9 Thread A 10
The output is definitely not a pattern, the pieces of codes are randomly run via threads.
Thread Using Thread Class
This is also one of the methods to implement the concept of threading in Java. We can create a child of thread class to do this way.
We will understand this better with the help of the example given below –
class Multi extends Thread{
public void run(){
System.out.println("thread is running...");
}
public static void main(String args[]){
Multi t1=new Multi();
t1.start();
}
}
Output-
Thread is Running
So, in This article, we learned about the concept of threading in Java and implementing it in two different ways.
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