线程的构造方法和TA的两种实现方式

1. 构造方法

1.1 示例程序

/**
 * @className: ThreadConstructor
 * @description: Thread Constructor
 **/
public class ThreadConstructor {

    public static void main(String[] args) {
        init();
    }

    private static void init() {
        // target runnable
        final Runnable targetRunnable = new Runnable() {
            @Override
            public void run() {
                // to do something
            }
        };
        // mainThread's threadGroup; default group is currentThread's parent GroupThread
        final ThreadGroup mainThreadGroup = Thread.currentThread().getThreadGroup();
        final String thread_04Name = "Thread-Constructor-04";
        final String thread_05Name = "Thread-Constructor-05";
        final String thread_06Name = "Thread-Constructor-06";
        final String thread_07Name = "Thread-Constructor-07";
        final String thread_08Name = "Thread-Constructor-08";
        // init stack size, Beyond method stack throw java.lang.*Error
        long stackSize = 1 << 24;

        Thread thread_01 = new Thread();
        Thread thread_02 = new Thread(targetRunnable);
        Thread thread_03 = new Thread(mainThreadGroup, targetRunnable);
        Thread thread_04 = new Thread(thread_04Name);
        Thread thread_05 = new Thread(mainThreadGroup, thread_05Name);
        Thread thread_06 = new Thread(targetRunnable, thread_06Name);
        Thread thread_07 = new Thread(mainThreadGroup, targetRunnable, thread_07Name);
        Thread thread_08 = new Thread(mainThreadGroup, targetRunnable, thread_08Name, stackSize);
        thread_01.start();
        thread_02.start();
        thread_03.start();
        thread_04.start();
        thread_05.start();
        thread_06.start();
        thread_07.start();
        thread_08.start();
        mainThreadGroup.list();
    }
}

1.2 入参说明

• targetRunnable
  是接口 Runnable 的实现，需要实现 run() 方法。线程交由 JVM 管理，线程启动后，可运行的线程会执行 run() 的内部逻辑。
• threadGroup
  线程组，用来管理线程的，由线程组成；线程对象创建时可指定所属线程组 threadGroup; 未指定线程组则当前子线程线程组默认沿用父线程的线程组
• name
  线程名称，默认名称为 Thread-index，index 属于[0, +∞)。线程名称支持自定义，允许重复，不可为空；线程 ID 自增唯一。
• stackSize
  指定方法栈大小，避免内存泄漏。超出指定大小则会抛出 java.lang.*Error

关键代码演示：

    private static long threadSeqNumber;
    private static synchronized long nextThreadID() {
        return ++threadSeqNumber;
    }
    private static int threadInitNumber;
    private static synchronized int nextThreadNum() {
        return threadInitNumber++;
    }
    public Thread() {
        init(null, null, "Thread-" + nextThreadNum(), 0);
    }
    private void init(ThreadGroup g, Runnable target, String name,
                      long stackSize) {
        init(g, target, name, stackSize, null, true);
    }
    private void init(ThreadGroup g, Runnable target, String name,
                      long stackSize, AccessControlContext acc,
                      boolean inheritThreadLocals) {
        // ... ...
        Thread parent = currentThread();
        SecurityManager security = System.getSecurityManager();
        if (g == null) {
            if (security != null) {
                g = security.getThreadGroup();
            }
            if (g == null) {
                g = parent.getThreadGroup();
            }
        }
        // ... ...
        this.group = g;
        this.daemon = parent.isDaemon();
        this.priority = parent.getPriority();
        /* Set thread ID */
        tid = nextThreadID();
    }

2. 两种实现方式

2.1 作为子类继承 Thread 类

class ThreadByExtendsThread extends Thread {
    @Override
    public void run() {
        // super.run() or custom to do something
        super.run();
    }
}

eg: 线程调用方式

    ThreadByExtendsThread thread = new ThreadByExtendsThread();
    thread.start();

2.2 作为实现类实现 Runnable 接口

class ThreadByImplementsRunnable implements Runnable {
    @Override
    public void run() {
        // custom to to something
    }
}

eg: 线程调用方式

    ThreadByImplementsRunnable runnable = new ThreadByImplementsRunnable();
    Thread thread = new Thread(runnable);
    thread.start();

附：官方文档

在线文档：https://docs.oracle.com/javase/8/docs/api/
离线文档：https://www.oracle.com/java/technologies/javase-jdk8-doc-downloads.html

Power By niaonao