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What does start() function do in multithreading in Java?
Introduction
In Java, concurrency and multithreading are fundamental concepts that facilitate simultaneous execution of two or more parts of a program to maximize the utilization of CPU. The start() method plays a pivotal role in this process. This article delves into the workings of the start() function in Java multithreading, explaining its purpose and significance.
Java Multithreading A Brief Overview
Multithreading is one of Java's core features, allowing multiple sequences of code, known as threads, to execute concurrently within a single program. By enabling concurrent execution, Java allows more efficient use of CPU resources, particularly on systems with multiple processors or cores.
Threads can be created in Java by extending the Thread class or implementing the Runnable interface. Once a Thread object is created, the start() method is used to initiate the thread's execution.
The start() Method in Java Multithreading
The start() method is part of the java.lang.Thread class. Its primary purpose is to create a new thread and execute the run() method of the Thread class or Runnable interface concurrently
Example
Here is a simple example −
public class MyThread extends Thread {
public void run() {
System.out.println("Thread is running");
}
public static void main(String[] args) {
MyThread t1 = new MyThread();
t1.start();
}
}
Output
Thread is running
In the above code, t1 is an instance of MyThread, which extends the Thread class. The start() method is invoked on t1, causing the run() method to execute in a separate thread.
The Significance of the start() Method
Calling the start() method is essential to initiate a separate call stack for the new thread. Here are some reasons why start() is crucial −
Begins parallel execution: The start() method signals the Java Virtual Machine (JVM) to allocate a new thread, which then executes the code inside the run() method. This allows the thread to operate independently and in parallel with the main thread.
Preserves multithreading: If the run() method is invoked directly instead of calling start(), it will execute in the same thread, contradicting the purpose of multithreading. The start() method ensures the run() method executes in a separate thread.
Regulates thread lifecycle: The start() method, apart from initiating the thread, also puts the thread in a "Runnable state". It allows the thread scheduler to manage this thread's execution in relation to other threads in the program
Understanding Thread Lifecycle and start()
Understanding the lifecycle of a thread in Java is key to comprehending the start() method's role. The thread lifecycle includes several states, such as New, Runnable, Running, Blocked, Waiting, Timed Waiting, and Terminated. When a new Thread object is created, it's in the New state. The start() method moves the thread to the Runnable state, from where the thread scheduler can transition it to the Running state.
Conclusion
The start() method in Java multithreading is a catalyst that sets the thread in motion. It plays a significant role in managing the thread's lifecycle and ensuring the parallel execution of the run() method. Understanding this fundamental function is essential to harness the power of multithreading in Java effectively, leading to highly efficient and performant applications.
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