Java Thread Class

Introduction

The Thread class in Java allows the creation and management of threads, enabling concurrent execution in applications.

Table of Contents

1. What is the Thread Class?
2. Common Methods
3. Examples of Using the Thread Class
4. Conclusion

1. What is the Thread Class?

The Thread class represents a thread of execution in a Java program. It provides methods to manage thread lifecycle, priority, and behavior.

2. Common Methods

• start(): Begins the execution of a thread.
• run(): Contains the code that defines the thread’s task.
• sleep(long millis): Causes the thread to sleep for a specified time.
• join(): Waits for the thread to finish execution.
• interrupt(): Interrupts the thread.
• isAlive(): Checks if the thread is still running.
• getId(): Returns the thread’s unique ID.
• getName(): Gets the name of the thread.
• setName(String name): Sets the name of the thread.
• getPriority(): Returns the thread’s priority.
• setPriority(int newPriority): Sets the thread’s priority.
• getState(): Returns the current state of the thread.
• yield(): Causes the currently executing thread to pause and allow other threads to execute.

3. Examples of Using the Thread Class

Example 1: Using start() and run()

class MyThread extends Thread {
    public void run() {
        System.out.println("Thread is running.");
    }
}

public class StartRunExample {
    public static void main(String[] args) {
        MyThread thread = new MyThread();
        thread.start(); // Starts the thread
    }
}

Output:

Thread is running.

Example 2: Using sleep()

public class SleepExample {
    public static void main(String[] args) {
        Thread thread = new Thread(() -> {
            try {
                System.out.println("Thread is sleeping for 2 seconds.");
                Thread.sleep(2000);
                System.out.println("Thread awake.");
            } catch (InterruptedException e) {
                System.out.println("Thread interrupted.");
            }
        });
        thread.start();
    }
}

Output:

Thread is sleeping for 2 seconds.
Thread awake.

Example 3: Using join()

public class JoinExample {
    public static void main(String[] args) {
        Thread thread = new Thread(() -> System.out.println("Thread finished execution."));
        thread.start();
        try {
            thread.join(); // Waits for the thread to finish
            System.out.println("Main thread resumed.");
        } catch (InterruptedException e) {
            System.out.println("Thread interrupted.");
        }
    }
}

Output:

Thread finished execution.
Main thread resumed.

Example 4: Using interrupt()

public class InterruptExample {
    public static void main(String[] args) {
        Thread thread = new Thread(() -> {
            try {
                Thread.sleep(5000);
            } catch (InterruptedException e) {
                System.out.println("Thread was interrupted.");
            }
        });
        thread.start();
        thread.interrupt(); // Interrupts the thread
    }
}

Output:

Thread was interrupted.

Example 5: Using isAlive()

public class IsAliveExample {
    public static void main(String[] args) {
        Thread thread = new Thread(() -> System.out.println("Thread is running."));
        thread.start();
        System.out.println("Is thread alive? " + thread.isAlive());
    }
}

Output:

Thread is running.
Is thread alive? true

Example 6: Using getId()

public class GetIdExample {
    public static void main(String[] args) {
        Thread thread = new Thread(() -> System.out.println("Thread ID: " + Thread.currentThread().getId()));
        thread.start();
    }
}

Output:

Thread ID: 20

Example 7: Using getName() and setName()

public class GetSetNameExample {
    public static void main(String[] args) {
        Thread thread = new Thread(() -> System.out.println("Thread name: " + Thread.currentThread().getName()));
        thread.setName("CustomThread");
        thread.start();
    }
}

Output:

Thread name: CustomThread

Example 8: Using getPriority() and setPriority()

public class GetSetPriorityExample {
    public static void main(String[] args) {
        Thread thread = new Thread(() -> System.out.println("Thread priority: " + Thread.currentThread().getPriority()));
        thread.setPriority(Thread.MAX_PRIORITY);
        thread.start();
    }
}

Output:

Thread priority: 10

Example 9: Using getState()

public class GetStateExample {
    public static void main(String[] args) {
        Thread thread = new Thread(() -> {});
        System.out.println("Thread state: " + thread.getState());
        thread.start();
        System.out.println("Thread state after start: " + thread.getState());
    }
}

Output:

Thread state: NEW
Thread state after start: RUNNABLE

Example 10: Using yield()

public class YieldExample {
    public static void main(String[] args) {
        Thread thread = new Thread(() -> {
            System.out.println("Thread yielding.");
            Thread.yield();
            System.out.println("Thread resumed.");
        });
        thread.start();
    }
}

Output:

Thread yielding.
Thread resumed.

4. Conclusion

The Thread class in Java provides a comprehensive set of methods for managing thread lifecycle, priority, and behavior. Understanding and using these methods effectively can enhance concurrent programming in Java applications.