Thread state, priority and daemon thread | Java multi-thread (4)

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Java Multithreading summary: Java multithreading

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The status of the thread

• New Threads that have not been started are in this state

• Runnable threads executing in the Java VIRTUAL Machine are in this state

• The thread waiting for a monitor lock is in this state.

• Waiting In this state when a thread is Waiting for another thread to perform a specific action.

• Timed Waiting A thread in this state is Waiting for another thread to perform an action.

• The Terminated thread is in this state.

• Code case

/** * Thread state */
public class TestThreadStatus{

    public static void main(String[] args) throws InterruptedException {
        // We use the lamda expression to start a thread
        Thread th = new Thread(()->{
            for (int i = 0; i <5 ; i++) {
                try {
                    Thread.sleep(100);

                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            System.out.println("/ / / / / / / / / / / / / / / /");
        });

        Thread.State state = th.getState();
        System.out.println("State of thread at creation +"+state);// Thread status

        th.start();// Start the thread
        state = th.getState();
        System.out.println("State of the thread at start +"+state);

        // Enter the thread state as long as the thread does not terminate
        while(state ! = Thread.State.TERMINATED){ Thread.sleep(100);
            state = th.getState();
            System.out.println("new+"+state); }}}Copy the code

• The execution result is as follows:

Priority of the thread

• Java provides a thread scheduler to monitor all threads in a program that enter the ready state after startup. The thread scheduler determines which threads should be scheduled for execution based on priority.

• The priority of a thread is represented by a number ranging from 1 to 10.

• Use the following methods to change or obtain the priority

  • getPriority().setPriority(int xxx)

• Code examples:

/** * Thread priority, not necessarily successful */
public class TestThreadPriority {
    public static void main(String[] args) {
        MyPriority myPriority = new MyPriority();
        Thread t1 = new Thread(myPriority);
        Thread t2 = new Thread(myPriority);
        Thread t3 = new Thread(myPriority);
        Thread t4 = new Thread(myPriority);
        Thread t5 = new Thread(myPriority);
        Thread t6 = new Thread(myPriority);
        // Set thread priority first
        t1.setPriority(1);
        t1.start();
        t2.setPriority(3);
        t2.start();
        t3.setPriority(6);
        t3.start();
        t4.setPriority(Thread.MAX_PRIORITY);// Priority =10
        t4.start();
        t5.setPriority(Thread.MIN_PRIORITY);// Priority =1
        t6.setPriority(9);
        t6.start();

        System.out.println("main"); }}class MyPriority implements Runnable{

    @Override
    public void run(a) {
        System.out.println(Thread.currentThread().getName()+"-- The thread has been executed! -"+Thread.currentThread().getPriority()); }}Copy the code

• The execution result is as follows:

Third, daemon thread

• Threads are divided into user threads and daemon threads

• The VM must ensure that the user thread is finished

• The VM does not have to wait for the daemon thread to finish executing

  • For example, recording operation logs in the background, monitoring memory, garbage collection and so on…

• Code case

public class TestDaemon {
    public static void main(String[] args) {
        God god = new God();
        You you=new You();
        Thread thread = new Thread(god);
        thread.setDaemon(true);// The default is flase for user threads and true for daemon threads
        thread.start();
        newThread(you).start(); }}class God implements Runnable{

    @Override
    public void run(a) {
        while (true){
            System.out.println("God is watching over you -------"); }}}class You implements Runnable{

    @Override
    public void run(a) {
        for (int i = 0; i <36500 ; i++) {
            System.out.println("Happy to live every day ------");
        }
        System.out.println("----goodbye! Beautiful World!!! -- -- -- -- -- -"); }}Copy the code

• The execution result is as follows:

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