Thread源碼淺析

一、Thread類的數據結構

class Thread implements Runnable {
    //...
    private char        name[];//線程的名字
    private int         priority;//線程的優先級
    //...
    /* Whether or not the thread is a daemon thread. */
    private boolean     daemon = false;  //標記是否爲守護線程
    /* What will be run. */
    private Runnable target;//線程類的父接口
    /* For autonumbering anonymous threads. */
    private static int threadInitNumber;//在匿名線程的時候使用
    //...
}

二、構造器

Thread有比較多的構造器,比較常用的如下:

public Thread()
public Thread(Runnable target)
public Thread(String name)
public Thread(Runnable target, String name)

三、線程的優先級的等級

/**
     * The minimum priority that a thread can have.
     */
    public final static int MIN_PRIORITY = 1;

   /**
     * The default priority that is assigned to a thread.
     */
    public final static int NORM_PRIORITY = 5;

    /**
     * The maximum priority that a thread can have.
     */
    public final static int MAX_PRIORITY = 10;

四、主要的方法

yield():提醒調度器當前線程放棄處理
sleep(long min):是線程睡眠min毫秒,這個線程將不會丟失鎖
start():啓動線程,JVM會調用run方法
interrupt():中斷線程
interrupted():判斷是否無邊框
isAlive():判斷線程是否還存活
join(long):等到直到線程死去,如果參數爲0，表示永久的等待->內部採用wait()實現

五、線程的啓動

第一種:
Thread t = SubThread();
t.start()
注:SubThread是繼承Thread的類
由於JVM會調用run方法
Thread類的run方法：

public void run() {
        if (target != null) {
            target.run();
        }
    }

默認構造器

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);
    }

可以知道target爲null
如果子類沒有重寫父類的run方法,JVM會調用一個空的run方法,一般使用線程都要重新run方法
第二種方式:
Thread t = Thread(new TestRun());
t.start()
注：TestRun實現了Runnable接口
先有必要看一下Runnable接口
Runnable接口很簡潔.

public
interface Runnable {
    /**
     * When an object implementing interface <code>Runnable</code> is used
     * to create a thread, starting the thread causes the object's
     * <code>run</code> method to be called in that separately executing
     * thread.
     * <p>
     * The general contract of the method <code>run</code> is that it may
     * take any action whatsoever.
     *
     * @see     java.lang.Thread#run()
     */
    public abstract void run();
}

run方法爲抽象方法,所以必須要實現run接口
這種實現可以得出：
1.可以得出target不爲空
2.target.run()會調用子類的run方法也就是TestRun類中實現的run方法。