This document introduces multithreading in Java, covering how to create and manage threads using the Thread class and Runnable interface. Learn about synchronization, thread states, and how to write concurrent programs with examples. Perfect for second-year Computer Science students.
1. What is Multithreading?
Multithreading is a concurrent execution technique where multiple threads
run independently but share the same resources, such as memory space.
Each thread performs a different task in the program simultaneously,
improving performance, especially on multi-core processors.
A thread is a lightweight process, and a Java program can have multiple
threads that run concurrently.
2. Thread Class and Runnable Interface
There are two main ways to create threads in Java:
o Extending the Thread class
o Implementing the Runnable interface
Using the Thread Class
You can create a thread by creating a subclass of the Thread class and
overriding its run() method.
Example:
class MyThread extends Thread {
public void run() {
System.out.println("Thread is running");
}
}
public class Main {
public static void main(String[] args) {
MyThread thread = new MyThread();
, thread.start(); // start() invokes the run() method
}
}
Using the Runnable Interface
You can also create a thread by implementing the Runnable interface and
passing an instance of the class to a Thread object.
Example:
class MyRunnable implements Runnable {
public void run() {
System.out.println("Thread is running");
}
}
public class Main {
public static void main(String[] args) {
MyRunnable runnable = new MyRunnable();
Thread thread = new Thread(runnable);
thread.start();
}
}
3. Thread Lifecycle
A thread in Java can be in one of the following states:
o New: The thread is created but not yet started.
o Runnable: The thread is ready to run and is waiting for CPU time.
o Blocked: The thread is waiting for a resource (like I/O operations or
synchronization).
o Waiting: The thread is waiting indefinitely for another thread to
perform a specific action.
o Terminated: The thread has finished executing.
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