java併發編程 日誌類demo

public class LogWriter {

    private long count = 0;

    private volatile boolean isShutDown;

    private final LogThread logThread;

    private final BlockingQueue<String> queue;

    public LogWriter(PrintWriter writer) {
        this.logThread = new LogThread(writer);
        this.queue = new LinkedBlockingQueue<>();
    }

    public void start() {
        logThread.start();
    }

    public void end() {
        // 中斷take阻塞
        logThread.interrupt();
        // 判斷是否停止，和interrupt區別，需要把日誌打印完，在停止線程
        isShutDown = true;
    }

    public void log(String message) {
        try {
            synchronized (this) {
                // 如果停止了，就不能在添加日誌
                if (isShutDown) {
                    throw new IllegalStateException("已關閉");
                }
                // 記錄日誌數量，在關閉的時候，打印完成
                count++;
            }
            queue.put(message);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

    }

    private class LogThread extends Thread {

        private PrintWriter writer;

        public LogThread(PrintWriter writer) {
            this.writer = writer;
        }

        @Override
        public void run() {
            try {
                while (true) {
                    try {
                        // 限判斷，在打印，判斷需要加鎖
                        synchronized (LogWriter.this) {
                            if (isShutDown && count == 0) {
                                break;
                            }
                        }
                        writer.println(queue.take());
                        // 64位機.long-- 操作並非原子，加鎖保證原子性和可見性
                        synchronized (LogWriter.this) {
                            count--;
                        }
                    } catch (InterruptedException e) {
                        // 繼續執行
                        e.printStackTrace();
                    }
                }
            } finally {
                writer.close();
            }
        }
    }

    public static void main(String[] args) {
        PrintWriter printWriter = new PrintWriter(System.out, true);
        LogWriter logWriter = new LogWriter(printWriter);
        logWriter.start();
        logWriter.log("test");
        logWriter.end();
        System.out.println("main end");
    }
}