使用带锁的多线程来实现文件的拷贝

最新推荐文章于 2024-08-17 08:37:57 发布

原创最新推荐文章于 2024-08-17 08:37:57 发布 · 296 阅读

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本文介绍了一种使用带锁的多线程技术进行文件拷贝的方法，通过一个线程读取文件，另一个线程写入文件，有效地提高了文件拷贝的效率。文章详细阐述了如何使用Lock和Condition来协调线程之间的读写操作，避免了数据竞争和死锁的问题。

使用带锁的多线程来实现文件的拷贝
一个线程读，一个线程写
使用Lock

设计逻辑

需要两个线程类实现Runnable接口
需一个功能类完成读和写的方法
使用构造方法传参

功能类

public class ThreadCopy {
	BufferedReader reader;
	BufferedWriter writer;
	boolean isRead=true;
	
	final Lock lock=new ReentrantLock();
	final Condition readCondition=lock.newCondition();
	final Condition writeCondition=lock.newCondition();
	public String hangString="";
	
	public ThreadCopy(BufferedReader reader, BufferedWriter writer) {
		super();
		this.reader = reader;
		this.writer = writer;
	}
	
	//读
	public void readHang() {
		System.out.println("=====读一行====");
		lock.lock();
		try {
			while (!isRead) {
				try {
					readCondition.await();
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
			
			try {
				hangString=reader.readLine();
				Thread.sleep(1000);
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			isRead=!isRead;
			writeCondition.signal();//唤醒对方
		} finally {
			lock.unlock();// TODO: handle finally clause
		}
	}
	//写
	public void writeHang() {
		lock.lock();
		
		try {
			while (isRead) {
				try {
					writeCondition.await();
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
			try {
				writer.write(hangString);
				writer.newLine();
				writer.flush();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			isRead=!isRead;
			readCondition.signal();
		} finally {
			lock.unlock();// TODO: handle finally clause
		}
	}
}

线程类

public class Readxc implements Runnable {
	ThreadCopy threadCopy;

	public Readxc(ThreadCopy threadCopy) {
		super();
		this.threadCopy = threadCopy;
	}

	@Override
	public void run() {
		// TODO Auto-generated method stub
		while (threadCopy.hangString!=null) {
			threadCopy.readHang();
		}
		
	}
	
}

public class Writexc implements Runnable {
	ThreadCopy threadCopy;

	public Writexc(ThreadCopy threadCopy) {
		super();
		this.threadCopy = threadCopy;
	}

	@Override
	public void run() {
		// TODO Auto-generated method stub
		while (threadCopy.hangString!=null) {
			threadCopy.writeHang();
		}
	}
	
}

测试类

public class Testio {

	public static void main(String[] args) throws IOException {
		// TODO Auto-generated method stub
//		使用带锁的多线程来实现文件的拷贝
//		
//		一个线程读，一个线程写
//		
//		使用Lock
		BufferedReader bufferedReader = new BufferedReader(new FileReader("D:\\1906\\JAVA1906\\day34\\gbk.txt"));
		BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter("D:\\1906\\JAVA1906\\day34\\gbk1copy.txt"));

		ThreadCopy threadCopy = new ThreadCopy(bufferedReader, bufferedWriter);
		
		Readxc readxc = new Readxc(threadCopy);
		Writexc writexc = new Writexc(threadCopy);
		
		Thread t1= new Thread(readxc);
		Thread t2= new Thread(writexc);
		t1.start();
		t2.start();
		
	}

}