How do I create a daemon thread?

By Wayan in Core API, Lang Package 0 Comment

A daemon thread is simply a background thread that is subordinate to the thread that creates it, so when the thread that created the daemon thread ends, the daemon thread dies with it. A thread that is not a daemon thread is called a user thread. To create a daemon thread, call setDaemon() method with a true boolean value as argument before the thread is started.

package org.kodejava.lang;

public class DaemonThread implements Runnable {
    private final String threadName;

    private DaemonThread(String threadName) {
        this.threadName = threadName;
    }

    public static void main(String[] args) {
        Thread t1 = new Thread(new DaemonThread("FirstThread"));
        Thread t2 = new Thread(new DaemonThread("SecondThread"));

        // t1 is as daemon thread
        t1.setDaemon(true);
        t1.start();

        // t2 is a user thread
        t2.start();
    }

    public void run() {
        System.out.println("Running [" + threadName + "]");
    }
}

How do I use the sleep method of the Thread class?

By Wayan in Core API, Lang Package 0 Comment

Here is another example that use the Thread.sleep() method. In the example we create two instances of the ThreadSleepAnotherDemo, we give each thread a name and the sleep interval so that we can see how to thread execution.

package org.kodejava.lang;

import java.util.Calendar;

public class ThreadSleep implements Runnable {
    private final String threadName;
    private final long sleep;

    public ThreadSleep(String threadName, long sleep) {
        this.threadName = threadName;
        this.sleep = sleep;
    }

    public static void main(String[] args) {
        Thread thread1 = new Thread(new ThreadSleep("FirstThread", 1000));
        Thread thread2 = new Thread(new ThreadSleep("SecondThread", 3000));

        // Start the threads
        thread1.start();
        thread2.start();
    }

    // The run() method will be invoked when the thread is started.
    public void run() {
        System.out.println("Start thread [" + this.threadName + "]");
        try {
            while (true) {
                // Pause the thread for "sleep" milliseconds.
                Thread.sleep(this.sleep);
                System.out.println("[" + threadName + "]" +
                        Calendar.getInstance().getTime());
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("Finish thread [" + this.threadName + "]");
    }
}

These are the sample output produced by the code snippet above:

Start thread [FirstThread]
Start thread [SecondThread]
[FirstThread]Mon Oct 25 11:52:13 CST 2021
[FirstThread]Mon Oct 25 11:52:14 CST 2021
[SecondThread]Mon Oct 25 11:52:15 CST 2021
[FirstThread]Mon Oct 25 11:52:15 CST 2021
[FirstThread]Mon Oct 25 11:52:16 CST 2021

How do I pause the current thread?

By Wayan in Core API, Lang Package 0 Comment

You can pause a current thread for a number of milliseconds by using the sleep() method of the Thread class. While the current thread is sleeping, it will allow other threads to execute.

package org.kodejava.lang;

public class ThreadSleepDemo implements Runnable {
    public static void main(String[] args) {
        Thread thread = new Thread(new ThreadSleepDemo());
        thread.start();
    }

    // The run() method will be invoked when the thread is started.
    public void run() {
        System.out.println("Start..");
        try {
            // Wait for 10 seconds
            Thread.sleep(10000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("Finish...");
    }
}

How do I start a thread execution?

By Wayan in Core API, Lang Package 0 Comment

To make a thread begin its execution, call the start() method on a Thread or Runnable instance. Then the Java Virtual Machine will calls the run method of this thread.

The snippet below is showing how to create a thread by implementing the Runnable interface.

package org.kodejava.lang;

public class ThreadRun implements Runnable {

    public static void main(String[] args) {
        // Instantiate ThreadRun
        ThreadRun runner = new ThreadRun();

        // Create instance of Thread and passing ThreadRun object
        // as argument.
        Thread thread = new Thread(runner);

        // By passing Runnable object, it tells the
        // thread to use run() of Runnable object.
        thread.start();
    }

    public void run() {
        System.out.println("Running..");
    }
}

The snippet below is showing how to create a thread by extending the Thread class.

package org.kodejava.lang;

public class ThreadStart extends Thread {

    public static void main(String[] args) {
        ThreadStart thread = new ThreadStart();

        // Start this thread
        thread.start();
    }

    /**
     * The run() method will be invoked when the thread is started.
     */
    @Override
    public void run() {
        System.out.println("Running..");
    }
}

How do I get current number of live threads?

By Wayan in Core API, Management 0 Comment 
package org.kodejava.lang.management;

import java.lang.management.ManagementFactory;
import java.lang.management.ThreadMXBean;

public class ThreadCount {

    public static void main(String[] args) {
        // Get the managed bean for the thread system of the Java
        // virtual machine.
        ThreadMXBean bean = ManagementFactory.getThreadMXBean();

        // Get the current number of live threads including both
        // daemon and non-daemon threads.
        int threadCount = bean.getThreadCount();
        System.out.println("Thread Count = " + threadCount);
    }
}