关于对synchronized的理解

 当一个线程进入一个对象的一个synchronized方法后，其它线程是否可进入此对象的其它方法?

今天在论坛中看见这道题，开始也很模糊，最后写了个程序得出如下答案。

如果是同步方法的话是不可以的。

如果是非同步方法的话是可以的。

下面贴出代码：

package Test;

public class Test1
{
public static void main(String[] args)
{
ThreadDemo threadDemo=new ThreadDemo();
Thread t1=new ThreadOne(threadDemo);
Thread t2=new ThreadTwo(threadDemo);
Thread t3=new ThreadThree(threadDemo);
t1.start();
t2.start();
t3.start();

}

}

class ThreadDemo
{

public synchronized void method1()
{
for (int i = 0; i < 10; i++)
{
try
{
Thread.sleep(500);
} catch (InterruptedException e)
{
e.printStackTrace();
}
System.out.println("同步方法1"+"    "+ i);
}
}

public synchronized void method2()
{
for (int i = 0; i < 10; i++)
{
try
{
Thread.sleep(500);
} catch (InterruptedException e)
{
e.printStackTrace();
}
System.out.println("同步方法2"+"    " + i);
}
}

public void Print()
{
for (int i = 0; i < 10; i++)
{
try
{
Thread.sleep(500);
} catch (InterruptedException e)
{
e.printStackTrace();
}
System.out.println("非同步方法" + i);
}
}
}

class ThreadOne extends Thread
{
private ThreadDemo threadDemo;

public ThreadOne(ThreadDemo threadDemo)
{
this.threadDemo = threadDemo;
}

public void run()
{
this.threadDemo.method1();
}
}

class ThreadTwo extends Thread
{
private ThreadDemo threadDemo;

public ThreadTwo(ThreadDemo threadDemo)
{
this.threadDemo = threadDemo;
}

public void run()
{
this.threadDemo.method2();
}
}

class ThreadThree extends Thread
{
private ThreadDemo threadDemo;

public ThreadThree(ThreadDemo threadDemo)
{
this.threadDemo = threadDemo;
}

public void run()
{
this.threadDemo.Print();
}

}

定义ThreadDemo类 有三个方法metho1，method2，Print。

其中metho1，method2为同步方法。Print为非同步方法。

如果在主函数中只开启t1.start()和t2.start();则输出结果为

t1输出完后，t2在输出。所以如果是同步方法的话是不可以的。

如果在主函数中只开启t1.start()和t3.start();则输出结果为

t1，Print交替输出。所以如果是非同步方法的话是可以的。

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