java 多线程开发三

于 2014-05-02 13:11:25 发布
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java 线程的死锁

多线程共享一个资源的时候需要同步但是过多的同步会导致死锁。

例如生产者和消费者的问题

public class Info {
	private String name="曹飞龙";
	private int age= 25;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
}

/**
 * 生产者
 * @author 曹飛龍 
 */
public class Producer implements Runnable {
	private Info info;
	public Producer(Info info) {
		super();
		this.info = info;
	}
	@Override
	public void run() {
		boolean flag = false;
		for (int i = 0; i < 25; i++) {
			if (flag) {
				this.info.setName("bob");
				try {
					Thread.sleep(1000);
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				this.info.setAge(20);
				flag = false;
			} else {
				this.info.setName("Marry");
				try {
					Thread.sleep(1000);
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				this.info.setAge(26);
				flag = true;
			}
		}
	}
}

/**
 * 消费者
 * @author 曹飞龙
 */
public class Consumer implements Runnable {
	private Info info;
	public Consumer(Info info) {
		super();
		this.info = info;
	}
	@Override
	public void run() {
		for (int i = 0; i < 25; i++) {
			try {
				Thread.sleep(1000);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			System.out.println("name:" + this.info.getName() + " age:"
					+ this.info.getAge());
		}
	}
}

/**
 * 测试类
 * @author 曹飞龙
 */
public class Test {
	public static void main(String[] args) {
		Info info = new Info();
		Producer producer = new Producer(info);
		Consumer consumer = new Consumer(info);
		new Thread(producer).start();
		new Thread(consumer).start();
	}

}

运行结果

name:bob age:26
name:Marry age:20
name:bob age:26
name:Marry age:20
name:bob age:26
name:Marry age:20
name:bob age:26
name:Marry age:20
name:bob age:26
name:Marry age:20
name:bob age:26
name:Marry age:20
name:bob age:26
name:Marry age:20
name:bob age:26
name:Marry age:20
name:bob age:26
name:Marry age:20
name:bob age:26
name:Marry age:20
name:bob age:26
name:Marry age:20
name:bob age:26
name:Marry age:20
name:Marry age:26

可以从结果中看出来姓名和年龄不能相互对应


那么如何解决呢？

加入同步

加入等待和唤醒


先看看加入同步会如何

public class Info {
	private String name = "曹飞龙";
	private int age = 25;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	//同步填入数据
	public synchronized void setInfo(String name, int age)
			throws InterruptedException {
		this.name = name;
		Thread.sleep(1000);
		this.age = age;
	}
	//同步获取数据
	public synchronized void getInfo() throws InterruptedException {
		Thread.sleep(1000);
		System.out.println("age:" + this.getAge() + " name:" + this.getName());
	}
}

/**
 * 生产者
 * 
 * @author 曹飛龍
 */
public class Producer implements Runnable {
	private Info info;
	public Producer(Info info) {
		super();
		this.info = info;
	}
	@Override
	public void run() {
		boolean flag = false;
		for (int i = 0; i < 25; i++) {
			if (flag) {
				try {
					info.setInfo("bob", 20);
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				flag = false;
			} else {
				try {
					info.setInfo("Marray", 26);
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				flag = true;
			}
		}
	}
}

/**
 * 消费者
 * 
 * @author 曹飞龙
 */
public class Consumer implements Runnable {
	private Info info;
	public Consumer(Info info) {
		super();
		this.info = info;
	}
	@Override
	public void run() {
		for (int i = 0; i < 25; i++) {
			try {
				info.getInfo();
			} catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}
}

/**
 * 测试类
 * @author 曹飞龙
 */
public class Test {
	public static void main(String[] args) {
		Info info = new Info();
		Producer producer = new Producer(info);
		Consumer consumer = new Consumer(info);
		new Thread(producer).start();
		new Thread(consumer).start();
	}
}
运行效果如下：

age:26 name:Marray
age:20 name:bob
age:20 name:bob
age:20 name:bob
age:20 name:bob
age:20 name:bob
age:26 name:Marray
age:26 name:Marray
age:20 name:bob
age:20 name:bob
age:26 name:Marray
age:26 name:Marray
age:26 name:Marray
age:20 name:bob
age:20 name:bob
age:26 name:Marray
age:26 name:Marray
age:26 name:Marray
age:26 name:Marray
age:26 name:Marray
age:26 name:Marray
age:26 name:Marray
age:26 name:Marray
age:26 name:Marray
age:26 name:Marray

现在年龄和姓名的之可以对应但是 出现了多次的重复打印

解决者个问题就需要使用Object类帮忙了、，我们可以使用其中的等待和唤醒操作。


public class Info {
	private String name = "曹飞龙";
	private int age = 25;
	private boolean flag = false;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	// 同步填入数据
	public synchronized void setInfo(String name, int age)
			throws InterruptedException {
		if (!flag) {
			super.wait();
		}
		this.name = name;
		Thread.sleep(1000);
		this.age = age;
		flag = false;
		super.notify();
	}
	// 同步获取数据
	public synchronized void getInfo() throws InterruptedException {
		if (flag) {
			super.wait();
		}
		Thread.sleep(1000);
		System.out.println("age:" + this.getAge() + " name:" + this.getName());
		flag = true;
		super.notify();
	}
}



/**
 * 生产者
 * 
 * @author 曹飛龍
 */
public class Producer implements Runnable {
	private Info info;
	public Producer(Info info) {
		super();
		this.info = info;
	}
	@Override
	public void run() {
		boolean flag = false;
		for (int i = 0; i < 25; i++) {
			if (flag) {
				try {
					info.setInfo("bob", 20);
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				flag = false;
			} else {
				try {
					info.setInfo("Marray", 26);
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				flag = true;
			}
		}
	}
}

/**
 * 消费者
 * 
 * @author 曹飞龙
 */
public class Consumer implements Runnable {
	private Info info;
	public Consumer(Info info) {
		super();
		this.info = info;
	}
	@Override
	public void run() {
		for (int i = 0; i < 25; i++) {
			try {
				info.getInfo();
			} catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}
}

/**
 * 测试类
 * @author 曹飞龙
 */
public class Test {
	public static void main(String[] args) {
		Info info = new Info();
		Producer producer = new Producer(info);
		Consumer consumer = new Consumer(info);
		new Thread(producer).start();
		new Thread(consumer).start();
	}
}

运行效果：

age:25 name:曹飞龙
age:26 name:Marray
age:20 name:bob
age:26 name:Marray
age:20 name:bob
age:26 name:Marray
age:20 name:bob
age:26 name:Marray
age:20 name:bob
age:26 name:Marray
age:20 name:bob
age:26 name:Marray
age:20 name:bob
age:26 name:Marray
age:20 name:bob
age:26 name:Marray
age:20 name:bob
age:26 name:Marray
age:20 name:bob
age:26 name:Marray
age:20 name:bob
age:26 name:Marray
age:20 name:bob
age:26 name:Marray
age:20 name:bob

--最后一部分我我自己也不是非常的理解  希望有人能够帮助理解一下


下边的仅仅工参考 有点晕

当生产者线程调用getInfo()同步方法是如果Info类中的flag为false 调用wait()方法使得 object 线程等待 

这个时候消费者线程调用getInfo()同步方法flag 为false 所以去的info 里边的姓名和年龄并且调用notify唤醒object线程把flag 标记标记为true

当生产者线程再次调用getInfo()同步方法flag 为true 为info 的姓名和年龄赋值



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