练手java thread(五)

通过Lock对象的lock()和unlock()方法来模拟synchronized待模块。

 

1.Lock lock = new ReentrantLock();

2.ReadWriterLock rwl = new ReentrantReadWriterLock();是用来维护读取与写入分离的lock，同时可以有多个线程持有readlock，因为read通常是安全的并发操作；但只有一个线程可以持有write lock。

(if a thread has a write lock,nobody can have read/write lock.）

 

入口类：

package thread.test05;

public class LockTest {
	public static void main(String[] args) {
		MyStack stack=new MyStack(20);
		Thread t1=new MyThreadA(stack);
		Thread t2=new MyThreadB(stack);
		t1.start();
		t2.start();
		
		try {
			Thread.sleep(10000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		System.out.println(stack);

	}
}

class MyThreadA extends Thread{
	private MyStack stack;
	
	public MyThreadA (MyStack stack){
		this.stack=stack;
	}
	
	public void run(){
		for(int i=0;i<10;i++){
			try {
				Thread.sleep(10);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			stack.push(i+"");
		}
	}
}

class MyThreadB extends Thread{
	private MyStack stack;
	
	public MyThreadB (MyStack stack){
		this.stack=stack;
	}
	
	public void run(){
		for(int i=0;i<10;i++){
			try {
				Thread.sleep(10);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			stack.push((char)('A'+i)+"");
		}
	}
}

 MyStack类如下：

package thread.test05;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class MyStack {
	private Object[] data;
	private int count;
	private Lock lock;
	
	public MyStack(int size){
		data=new Object[size];
		count=0;
		lock=new ReentrantLock();
	}
	
	public void push(Object obj){
		lock.lock();
		try{
			if(count==data.length){
				throw new FullStackException("栈空间已满!");
			}
			data[count]=obj;
			try {
				Thread.sleep(10);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			count++;
		}
		finally{
			lock.unlock();
		}

	}
	
	public String toString(){
		StringBuffer sb=new StringBuffer();
		for(int i=0;i<count;i++){
			sb.append(data[i]+",");
		}
		return sb.toString();
	}

}

经测试，MyStack中的数据不会发生混乱。

 //////////////////////////////////////////

读写锁：

 

package thread.test05;

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

public class LockTest2 {
	private final ReadWriteLock rwl = new ReentrantReadWriteLock();
	private final Lock r = rwl.readLock();
	private final Lock w = rwl.writeLock();
	
	
}