Руководство по Java Core. Многопоточность. Основные операции.

Язык программирования Java обеспечивает полный контроль над многопоточными приложениями. Благодаря этому мы можем разрабатывать многопоточные программы, которые ведут себя именно так, как нам это необходимо.

С полным списком таких методов вы можете ознакомиться в официальной документации.

Рассмотрим пример простого приложения.

Пример:

Класс ThreadControl

public class ThreadControl implements Runnable {
    public Thread thread;
    private String threadName;
    boolean suspended = false;

    ThreadControl(String name) {
        threadName = name;
        System.out.println("Thread " + threadName + " successfully created.");
    }

    public void run() {
        System.out.println("Thread " + threadName + " is running...");
        try {
            for (int i = 1; i <= 5; i++) {
                System.out.println("Thread " + threadName + " " + i);

                Thread.sleep(300);
                synchronized (this) {
                    while (suspended) {
                        wait();
                    }
                }
            }
        } catch (InterruptedException e) {
            System.out.println("Thread " + threadName + " is interrupted.");
        }
        System.out.println("Leaving thread " + threadName + "...");
    }

    public void start() {
        System.out.println("Starting " + threadName + " thread...");
        if (thread == null) {
            thread = new Thread(this, threadName);
            thread.start();
        }
    }

    void suspend() {
        suspended = true;
    }

    synchronized void resume() {
        suspended = false;
        notify();
    }
}

Класс ThreadControlDemo

public class ThreadControlDemo {
    public static void main(String args[]) {

        ThreadControl threadOne = new ThreadControl( "Thread One");
        threadOne.start();

        ThreadControl threadTwo = new ThreadControl( "Thread Two");
        threadTwo.start();

        try {
            Thread.sleep(1000);
            threadOne.suspend();
            System.out.println("Thread One suspended...");
            Thread.sleep(1000);
            threadOne.resume();
            System.out.println("Thread One activated");
            threadTwo.suspend();
            System.out.println("Thread Two suspended...");
            Thread.sleep(1000);
            threadTwo.resume();
            System.out.println("Thread Two activated");
        } catch (InterruptedException e) {
            System.out.println("Main thread is interrupted...");
        }
        try {
            System.out.println("Standing by for finishing threads.");
            threadOne.thread.join();
            threadTwo.thread.join();
        } catch (InterruptedException e) {
            System.out.println("Main thread is interrupted...");
        }
        System.out.println("Leaving main thread...");
    }
}

В результате работы программы, мы получим, примерно, следующий результат:

/*Some System Messages*/

Thread Thread One successfully created.
Starting Thread One thread...
Thread Thread Two successfully created.
Starting Thread Two thread...
Thread Thread One is running...
Thread Thread One 1
Thread Thread Two is running...
Thread Thread Two 1
Thread Thread One 2
Thread Thread Two 2
Thread Thread One 3
Thread Thread Two 3
Thread Thread One 4
Thread Thread Two 4
Thread One suspended...
Thread Thread Two 5
Leaving thread Thread Two...
Thread One activated
Thread Thread One 5
Thread Two suspended...
Leaving thread Thread One...
Thread Two activated
Standing by for finishing threads.
Leaving main thread...

В этом разделе мы ознакомились с основами управления многопоточными приложениями.