synchronized 簡單理解實例

實例一、靜態方法的同步處理

public class DataCopyA {
	public static void main(String[] args) {
        task(0, 5*1000*1);
        DataCopyB.task(0, 5 * 1000 * 1);
	}
	public static void task(long time, long time2) {
		Timer timer = new Timer();
		TimerTask task = new TimerTask() {
			@Override
			public void run() {
				String str ="DataCopy-A";
                //斷點打於此處，進入方法體就會阻塞DataCopy-B的輸出
				DataCopyA.selectSql(str);
			}
		};
		timer.schedule(task, time, time2);
	}
	
	protected synchronized static void selectSql(String str) {
		System.out.println("--------------------");
		System.out.println(Thread.currentThread());
		System.out.println(str);
	}
	
}

public class DataCopyB {
	public static void task(long startTime, int time2) {
		Timer timer = new Timer();
		TimerTask task = new TimerTask() {
			@Override
			public void run() {
				String str ="CopyData-B";
				DataCopyA.selectSql(str);
			}
		};
		timer.schedule(task, startTime, time2);
	}
}

實例二、對同一對象的非靜態方法處理

public class DataCopyA {
	private DataCopyA() {}
	private static DataCopyA dataCopyA = new DataCopyA();
	public static DataCopyA getInstance() {
		return dataCopyA;
	}
	public static void main(String[] args) {
        task(0, 5*1000*1);
        DataCopyB.task(0, 5 * 1000 * 1);
	}
	public static void task(long time, long time2) {
		Timer timer = new Timer();
		TimerTask task = new TimerTask() {
			@Override
			public void run() {
				String str ="DataCopy-A";
                //斷點打於此處，進入方法體就會阻塞DataCopy-B的輸出
				DataCopyA.getInstance().selectSql(str);
			}
		};
		timer.schedule(task, time, time2);
	}
	
	protected synchronized void selectSql(String str) {
		System.out.println("--------------------");
		System.out.println(Thread.currentThread());
		System.out.println(str);
	}
	
}

public class DataCopyB {
	public static void task(long startTime, int time2) {
		Timer timer = new Timer();
		TimerTask task = new TimerTask() {
			@Override
			public void run() {
				String str ="CopyData-B";
				DataCopyA.getInstance().selectSql(str);
			}
		};
		timer.schedule(task, startTime, time2);
	}
}