java模拟实现简单的读写锁_java 实现简易读写锁-优快云博客

本文链接：https://blog.youkuaiyun.com/bq1073100909/article/details/48414087

本文通过使用数组和简单的锁操作实现并发控制，详细解释了如何在读写操作中控制多个线程的访问，确保数据的一致性和完整性。

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当一个文件进行读的时候，其他线程也可以进行读，但是不能写入，当一个文件进行写的时候，其他线程不能读和写。

我将使用一个数组形式的数据模拟读写的简单锁操作进行控制。

package org.dyb.readwrite;

public class DataHandler {
    private char[] buffer = "AAAAAAAAAAA".toCharArray();
    
    private ReadWriteLock rwl = new ReadWriteLock();
    
    public char[] read(String name) {
        System.out.println(name + "waiting for read ...");
        rwl.readLock();
        try {
            char[] data = doRead();
            System.out.println(name + "reads data " + new String(data));
            return data;
        } finally{
            rwl.readUnlock();
        }
    }
    
    public void write(String name,char[] data){
        System.out.println(name + "waiting for write ...");
        rwl.writeLock();
        try {
            System.out.println(name + "reads data " + new String(data));
            doWrite(data);
        }finally{
            rwl.writeUnlock();
        }
        
    }
    
    
    private char[] doRead(){
        char[] ret = new char[buffer.length];
        for(int i=0;i<buffer.length;i++){
            ret[i] = buffer[i];
            sleep(3);
        }
        return ret;
    }
    private void doWrite(char[] data){
        buffer = new char[data.length];
        for(int i=0;i<data.length;i++){
            buffer[i] = data[i];
            sleep(10);
        }
    } 

    private void sleep(int ms) {
        try {
            Thread.sleep(ms);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
    
    
}

在读写的操作上进行加锁。

package org.dyb.readwrite;

public class ReadWriteLock {
    
    private int readingThreads = 0;
    private int writingThreads = 0;
    private int waitingThreads = 0;
    
    private boolean preferWrite = true;
    
    public synchronized void readLock(){
        while(writingThreads>0||(preferWrite&&waitingThreads>0)){
            try {
                this.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        readingThreads++;
    }
    
    public synchronized void readUnlock(){
        readingThreads--;
        preferWrite = true;
        notifyAll();
    }
    
    public synchronized void writeLock(){
        waitingThreads++;
        while(readingThreads>0||writingThreads>0){
            try {
                this.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }finally{
                waitingThreads--;
            }
        }
        writingThreads++;
    }
    
    public synchronized void writeUnlock(){
        writingThreads--;
        preferWrite = false;
        notifyAll();
    }
    
}