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.
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.
Methods of Multithreading in Java
Following are the methods for Multithreading in Java.
|
start() |
The start method initiates the execution of a thread |
|
currentThread() |
The currentThread method returns the reference to the currently executing thread object. |
|
run() |
The run method triggers an action for the thread |
|
isAlive() |
The isAlive method is invoked to verify if the thread is alive or dead |
|
sleep() |
The sleep method is used to suspend the thread temporarily |
|
yield() |
The yield method is used to send the currently executing threads to standby mode and runs different sets of threads on higher priority |
|
suspend() |
The suspend method is used to instantly suspend the thread execution |
|
resume() |
The resume method is used to resume the execution of a suspended thread only |
|
interrupt() |
The interrupt method triggers an interruption to the currently executing thread class |
|
destroy() |
The destroy method is invoked to destroy the execution of a group of threads |
|
stop() |
The stop method is used to stop the execution of a thread |
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.
Multiprocessing vs. Multithreading in Java
The following table explains the fundamental differences between Multiprocessing and Multithreading in Java
Multiprocessing |
Multithreading |
|
Multiprocessing requires multiple physical processors for executing a complex process. |
Multithreading in Java requires virtual threads. These threads are independent of each other. |
|
Multiprocessing involves two types, namely symmetric and asymmetric multiprocessing. |
There are no different types of multithreading in Java |
|
Multiprocessing is heavy and time-consuming |
Multithreading in Java is completely light and a timesaving procedure |
|
In multiprocessing, each process owns a separate memory location |
In the process of Multithreading in Java, Threads share the same memory location |
|
If one processor is compromised, then the respective process of that CPU or the entire process may collapse |
Since all the threads are independent of each other, if any thread is compromised, then the entire process will not be affected by any means. |
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
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