What is a Thread in Java?

Thread in java – Threads help software to work more effectively by allowing it to do numerous tasks at once. Threads allow complex activities to be complete in the background without interrupting the main program.

In the context of Java, a thread is the path taken when running a program. Every Java application has at least one thread, referred to as the main thread, which is produced by the Java Virtual Machine (JVM) when the main() function is called with the main thread.

Thread in Java is creates by extending a class and implementing an interface. The java.lang library creates and manages all Java threads. Thread is a type of thread.

A single-threaded application can only handle one task at a time and has only one thread. Multi-threading is use to manage numerous tasks in parallel: multiple threads are form, each doing a different task.

How to Troubleshoot Java Application Issues

  • For faster background/batch job processing: When numerous tasks must be complete at the same time, multi-threading permits the tasks to run in parallel. As a result, the overall processing time is lower.
  • To take advantage of current CPUs: Modern systems typically include many processors, each with multiple cores. Multi-threading allows separate threads to be execute by different processors, allowing for more effective use of system resources.
  • In order to reduce response times, users want program to respond quickly. Response time can be lower by splitting down the processing required for a request into smaller pieces and having different threads do the processing in parallel.
  • To serve a large number of people at the same time: Thousands of users are expectes to use application servers like Tomcat, JBoss, Oracle WebLogic, and IBM WebSphere at the same time. The only way to accomplish this is by multithreading. Each request is handle by a single thread which creates by the application server.

How to create a thread in Java

A thread can be made in two ways.

It’s possible to make one by extending the Thread class and overriding the run() method:

Thread class:

Constructors and methods for creating and operating on threads are provided by the Thread class. The Thread class is a subclass of Object that implements the Runnable interface.

Commonly used Constructors of Thread class:

  • Thread()
  • Thread(String name)
  • Thread (Runnable r)
  • Thread (Runnable r, String name)

Commonly used methods of Thread class:

  • run() is a public void function that executes thread-specific actions.
  • start() is a public void that begins the thread’s execution.
  • The thread is called by JVM’s run() function.
  • public void sleep(long milliseconds): Sleeps the currently running thread for the provided number of milliseconds.
  • join() is a public void function that waits for a thread to die before continuing.
  • public void join(long milliseconds): waits for the specified milliseconds for a thread to die.
  • The priority of the thread is return via public int getPriority().
  • int set public
  • Changes the thread’s priority using priority(int priority).
  • getName() returns the thread’s name, which is a public String.
  • Changes the thread’s name with public void setName(String name).
  • currentThread() returns a reference to the thread that is presently running.
  • The thread’s id is return by public int getId().
  • a thread that is open to the public
  • The thread’s state is return via getState().
  • isAlive() is a public Boolean function that determines whether or not a thread is alive.
  • yield() is a public void function that returns the result of a calculation.

Runnable interface:

Any class with instances that are meant to be run by a thread should implement the Runnable interface. Only one method named run exists in the Runnable interface().

  • public void run(): is use to perform action for a thread.

Starting a thread in Java

A newly formed thread is starts using the start() function of the Thread class. Its functions are as follows:

  • A new thread has begun (with new callstack).
  • The thread transitions from the New to the Runnable stage.
  • The thread’s target run() method will be call when it has a chance to execute.

Example 01: Java Thread Example by extending Thread class

class Java_Thread extends Thread{  
public void run(){  
System.out.println("thread is running...");  
public static void main(String args[]){  
Java_Thread thread =new Java_Thread ();  



Example 02: Java Thread Example by implementing Runnable interface

class Runnable_thread implements Runnable{  
public void run(){  
System.out.println("thread is running...");  
public static void main(String args[]){  
Runnable_thread multi=new Runnable_thread ();  
Thread thread =new Thread(multi);  



Example 03: Using the Thread Class: Thread(String Name) – We can directly use the Thread class to spawn new threads using the constructors defined above.

class SoftHuntThread
public static void main(String argvs[])  
Thread thread= new Thread("Softhunt Thread");   
String string = thread.getName();  



Why Should You Monitor Thread in Java?

Hundreds of thousands of threads can run in parallel in a Java application in production. When a problem is discover. For example, the JVM is using a lot of CPU resources – the next question is: which thread is generating the CPU spike? Then there’s the question of which code snippet the thread is running. While it’s critical to disclose this data in real-time, it’s equally critical to make these details available for historical review. For example, your program may have experienced a CPU surge at 2 a.m. and been unusable, necessitating a server restart by your operations team. While this would have temporarily remedied the problem, what caused it in the first place, and how can we prevent it from happening again? Knowing what threads were executing in the JVM at 2 a.m. and which thread was consuming CPU is crucial to diagnosing the application performance issue.

Examine the JVM stack trace to determine which thread is causing the high CPU utilization.

In a JVM, multiple threads can be doing the same thing. When a request is processed, for example, a configuration file may need to be modified. Because numerous threads access the same configuration file, thread synchronization is require so that only one thread can update the configuration file at any given moment. While synchronization assures the constancy of a shared resource (in this case, the configuration file), it also adds the risk of delays in request processing. An application server must wait until the matching thread is allowed to enter the synchronized block before processing requests. Excessive use of synchronized blocks might cause a significant portion of a request’s processing time to be spent waiting for access to synchronized code blocks. It’s critical to keep thread synchronization blocking to a minimum in order to provide a nice user experience.

At the same time, keeping track of the number of threads generated in the JVM is critical. If a large number of threads are creates simultaneously, the JVM memory must be large enough to manage the load. Otherwise, the performance of the application will suffer. Administrators must also keep track of thread leaks, which occur when the number of threads in the JVM continues to grow, eventually causing the JVM to crash.

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