線程的生命周期（6 種狀态）

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線程的 6 種狀态

• New：已建立，未啟動，已做好準備工作
• Runnable：可運作的，調用start()方法後
• Blocked：阻塞，進入synchronized相關方法或代碼塊，未持有鎖

• Waiting：進入等待狀态（wait(), join(), park()），同樣喚醒方法（notify(), notifyAll(),

  unpark(), 其中join方法要等到join執行的線程執行完畢才被喚醒）

• Timed Waiting：計時等待，需要指定時間參數，可提前被喚醒，或者等待逾時後
• Terminated：終止，run方法執行完畢；出現未捕獲的異常意外終止

Blocked、Waiting、TimedWaiting都成為阻塞狀态

代碼示範

New / Runnable / Terminated 狀态

public class NewRunnableTerminated implements Runnable{
    @Override
    public void run() {
        for (int i = 0; i < 1000; i++) {
            System.out.println(i);
        }
    }

    public static void main(String[] args) {
        Thread thread = new Thread(new NewRunnableTerminated());
        // 建立線程，未啟動
        System.out.println(thread.getState());
        thread.start();
        // 啟動線程，可能還未運作
        System.out.println(thread.getState());
        try {
            Thread.sleep(10);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        // 已運作
        System.out.println(thread.getState());

        try {
            Thread.sleep(200);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        // 運作完畢
        System.out.println(thread.getState());
    }
}      

結果展示

Blocked / Waiting / TimedWaiting 狀态

public class BlockedWaitingTimedWaiting implements Runnable{
    @Override
    public void run() {
        syn();
    }
    private synchronized void syn() {
        try {
            Thread.sleep(1000);
            wait();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        BlockedWaitingTimedWaiting runnable = new BlockedWaitingTimedWaiting();
        Thread thread01 = new Thread(runnable);
        thread01.start();
        Thread thread02 = new Thread(runnable);
        thread02.start();
        try {
            Thread.sleep(100);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        // 線程1正在執行 Thread.sleep(1000)，狀态為 TIMED_WAITING
        System.out.println(thread01.getName() + ": " + thread01.getState());
        // 線程2未拿到鎖，處于 BLOCKED 狀态
        System.out.println(thread02.getName() + ": " + thread02.getState());
        try {
            Thread.sleep(1400);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        // wait() 使得進入 WAITING 狀态
        System.out.println(thread01.getName() + ": " + thread01.getState());
    }
}