Learn Multithreading in Java With Examples

Multithreading in Java is an act of executing a complex process using virtual processing entities independent of each other. These entities are called threads. Threads in Java are virtual and share the same memory location of the process. As the threads are virtual, they exhibit a safer way of executing a process.

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What are Multitasking and the Types of Multitasking?

Multitasking is an approach to minimize execution time and maximize CPU utilization by executing multiple tasks simultaneously. You can achieve the process of multitasking in Java using two methods, as described below.

Multiprocessing in Java 

Multiprocessing in Java is purely based on the number of processors available on the host computer. Every process initiated by the user is sent to the CPU (processor). It loads the registers on the CPU with the data related to the assigned process.

To perform multiprocessing in Java, the user needs one processor. Therefore, when the user requests the simultaneous execution of the second process, the alternate CPU core gets triggered and executes the process.

Multithreading in Java

Multithreading in Java is a similar approach to multiprocessing. However, there are some fundamental differences between the two. Instead of a physical processor, multithreading involves virtual and independent threads.

It assigns each process with one or more threads based on their complexity. Each thread is virtual and independent of the other. This makes process execution much safer. If a thread or two are terminated during an unexpected situation, the process execution will not halt.

In the next section of this Multithreading in Java tutorial, you will learn about a thread in Java.

What is a Thread in Java?

A thread is the smallest segment of an entire process. A thread is an independent, virtual and sequential control flow within a process. In process execution, it involves a collection of threads, and each thread shares the same memory. Each thread performs the job independently of another thread. 

Sometimes, the processes might be interdependent for an intermediate result to finish the process.

In the next part of the Multithreading in Java tutorial, you will learn about the Lifecycle of a Thread.

Lifecycle of a Thread in Java

The lifecycle of each thread in Java has five different stages. You will look into each one of those stages in detail. The Stages of the Lifecycle are mentioned below.

• New
• Runnable
• Running
• Waiting
• Dead

New

The first stage is "New". This stage is where it initiates the thread. After that, every thread remains in the new state until the thread gets assigned to a new task.

Runnable

The next stage is the runnable stage. Here, a thread gets assigned to the task and sets itself for running the task. 

Running

The third stage is the execution stage. Here, the thread gets triggered as control enters the thread, and the thread performs a task and continues the execution until it finishes the job. 

Waiting

At times, there is a possibility that one process as a whole might depend on another. During such an encounter, the thread might halt for an intermediate result because of its dependency on a different process. This stage is called the Waiting Stage.

Dead

The final stage of the process execution with Multithreading in Java is thread termination. After it terminates the process, the JVM automatically declares the thread dead and terminates the thread. This stage is known as the dead thread stage.

Now that you learned about the thread and its life cycle, move ahead and understand multithreading in Java.

What is Multithreading in Java?

So far, you have looked into the process, thread, and thread lifecycle. You understood that a computer executes a task via a thread. Now, you will learn the process of multithreading in Java.

As the name suggests, multithreading in Java executes a complex process by running a collection of threads simultaneously. Each thread belongs to the Java.lang.Thread class. The thread class overrides the run() method and executes the process.

In the next part, you will get to know about the methods of Multithreading in Java. 

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Methods of Multithreading in Java

Following are the methods for Multithreading in Java.

After the methods of Multithreading in Java, you will go through an example based on Multithreading in Java.

Example for Multithreading in Java

The following is an example based on multithreading in Java using the runnable interface.

//Code

package multithreading;

class ThreadCount extends Thread{

ThreadCount(){

super("Overriding Thread Class");

System.out.println("New thread created" + this);

start();

}

public void run(){ //Run Method

    try{

        for (int i=0 ;i<10;i++){

System.out.println("New thread created" + this);

Thread.sleep(1500);

        }

    }

    catch(InterruptedException e){

System.out.println("Currently executing thread is interrupted");

}

System.out.println("Currently executing thread run is terminated" );

}

}

public class MultiThreading{

public static void main(String args[]){

ThreadCount C = new ThreadCount();

try{

while(C.isAlive()){

System.out.println("Main Method Thread will be alive, until it's Child Thread stays alive");

Thread.sleep(2500); //Sleep method

}

}

catch(InterruptedException e){

System.out.println("Main Method thread is interrupted");

}

System.out.println("Main Method's thread run is terminated" );

}

}

//Output:

New thread createdThread[Overriding Thread Class,5,main]

Main Method Thread will be alive, until it's Child Thread stays alive

New thread createdThread[Overriding Thread Class,5,main]

New thread createdThread[Overriding Thread Class,5,main]

Main Method Thread will be alive, until it's Child Thread stays alive

New thread createdThread[Overriding Thread Class,5,main]

New thread createdThread[Overriding Thread Class,5,main]

Main Method Thread will be alive, until it's Child Thread stays alive

New thread createdThread[Overriding Thread Class,5,main]

Main Method Thread will be alive, until it's Child Thread stays alive

New thread createdThread[Overriding Thread Class,5,main]

New thread createdThread[Overriding Thread Class,5,main]

Main Method Thread will be alive, until it's Child Thread stays alive

New thread createdThread[Overriding Thread Class,5,main]

New thread createdThread[Overriding Thread Class,5,main]

Main Method Thread will be alive, until it's Child Thread stays alive

New thread createdThread[Overriding Thread Class,5,main]

Main Method Thread will be alive, until it's Child Thread stays alive

Currently executing thread run is terminated

Main Method's thread run is terminated

Next, you will learn the differences between multiprocessing and multithreading in java.

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Multiprocessing vs. Multithreading in Java

The following table explains the fundamental differences between Multiprocessing and Multithreading in Java

Next, you will learn about the advantages and disadvantages of multithreading in java.

Advantages of Multithreading in Java

Mentioned below are the few advantages of Multithreading in Java:

• Multithreading in Java improves the performance and reliability
• Multithreading in Java minimizes the execution period drastically
• There is a smooth and hassle-free GUI response while using Multithreading in Java
• The software maintenance cost is lower
• The CPU and other processing resources are modes judiciously used

Disadvantages of Multithreading in Java

Following are a few disadvantages of Multithreading in Java:

• Multithreading in Java poses complexity in code debugging
• Multithreading in Java increases the probability of a deadlock in process execution 
• The results might be unpredictable in some worst-case scenarios
• Complications might occur while code is being ported 

With that, you have come to an end of the “Multithreading in Java” tutorial.

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Conclusion

Java Development Kit could be your next step in the journey of learning Java. JDK is the fundamental tool in Java which includes the Java Run-time Environment and Java Virtual Machine.

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