Java併發編程入門（八）線程生命週期

時間 2019-11-07

標籤 java 併發編程入門線程生命週期欄目 Java 简体版

原文原文鏈接

Java極客 | 做者 / 鏗然一葉這是Java極客的第 36 篇原創文章

1、線程生命週期一

線程生命週期以下：java

1.線程建立後狀態爲NEW 2.線程啓動後狀態從NEW變爲RUNNABLE 3.線程調用同步代碼塊未得到同步鎖時狀態爲BLOCK，若是獲取到鎖則狀態爲RUNNABLE 4.線程運行結束後狀態爲TERMINATED

驗證代碼以下：編程

public class LifeCycleDemo {

    public static void main(String[] args) {
        Thread t0 = new Thread(new Runnable() {
            public void run() {
                Counter.increase();
            }
        });

        Thread t1 = new Thread(new Runnable() {
            public void run() {
                Counter.increase();
            }
        });

        //建立後狀態爲NEW
        printState(t0);
        printState(t1);

        t0.start();
        t1.start();

        //啓動後狀態爲RUNNABLE
        printState(t0);
        printState(t1);

        sleep(1000);

        //運行後t0得到同步鎖，進入代碼塊執行Thread.sleep後狀態變爲TIMED_WAITING，t1等待獲取同步鎖，狀態爲BLOCKED
        printState(t0);
        printState(t1);

        sleep(4000);

        //線程執行完後狀態爲TERMINATED
        printState(t0);
        printState(t1);

        System.out.println("count: " + Counter.getCount());
    }

    private static void printState(Thread t) {
        System.out.println(t.getName() + " " + t.getState());
    }

    private static void sleep(long millis) {
        try {
            Thread.sleep(millis);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

class Counter {
    private static int count;

    public synchronized static void increase() {
        count = count +1;

        try {
            //模擬併發爭用
            Thread.sleep(2000);
        } catch (InterruptedException ie) {
            ie.printStackTrace();
        }
    }

    public static int getCount() {
        return count;
    }
}
複製代碼

打印日誌：緩存

Thread-0 NEW
Thread-1 NEW
Thread-0 RUNNABLE
Thread-1 RUNNABLE
Thread-0 BLOCKED
Thread-1 TIMED_WAITING
Thread-0 TERMINATED
Thread-1 TERMINATED
count: 2
複製代碼

2、線程生命週期二

驗證代碼以下：安全

public class LifeCycleDemo2 {
    public static void main(String[] args) {
        Thread t0 = new Thread(new ChildThread(Thread.currentThread()));

        t0.start();
        //子線程啓動後狀態爲RUNNABLE
        printState(t0);

        try {
            //子線程join後，主線程狀態爲WAITING
            t0.join();

            //主線程狀態爲RUNNABLE
            printState(Thread.currentThread());

            //子線程運行結束，狀態爲TERMINATED
            printState(t0);

        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    private static void printState(Thread t) {
        System.out.println(t.getName() + " " + t.getState());
    }
}

class ChildThread implements Runnable {

    Thread parentThread;

    public ChildThread(Thread parentThread) {
        this.parentThread = parentThread;
    }
    public void run() {
        try {
            Thread.sleep(2000);
            //這裏是在子線程join以後打印，此時主線程狀態爲WAITING
            System.out.println(parentThread.getName() + " " + parentThread.getState());
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}
複製代碼

輸出日誌：bash

Thread-0 RUNNABLE
main WAITING
main RUNNABLE
Thread-0 TERMINATED
複製代碼

其餘場景不在單獨列出代碼。併發

3、線程生命週期三

這裏和前面的區別是方法參數中增長了時間參數，再也不舉例驗證。

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