Java多线程之读写锁分离设计模式

Java多线程之读写锁分离设计模式

主要完成任务：

1.read read 并行化

2.read write 不允许

3.write write 不允许

public class ReaderWorker extends Thread {

private final SharedData data;

public ReaderWorker(SharedData data) {

this.data = data;

}

@Override

public void run() {

while (true) {

try {

char[] readBuf = data.read();

System.out.println(Thread.currentThread().getName() + " reads " + String.valueOf(readBuf));

} catch (InterruptedException e) {

e.printStackTrace();

}

}

}

}

public class ReadWriteLock {

/**

* 当前有几个线程 在对它进行读操作

*/

private int readingReaders = 0;

/**

* 当前有几个线程 等待读操作

*/

private int waitingReaders = 0;

/**

* 当前有几个线程 正在写操作

*/

private int writingWriters = 0;

/**

* 当前有几个线程 正在写操作

*/

private int waitingWriters = 0;

/**

* 偏向于写

*/

private boolean preferWriter = true;

public ReadWriteLock() {

this(true);

}

public ReadWriteLock(boolean preferWriter) {

this.preferWriter = preferWriter;

}

public synchronized void readLock() throws InterruptedException {

this.waitingReaders++;

try {

/**

* 让写的线程先运行

*/

while (writingWriters > 0||(preferWriter&&waitingWriters>0)) {

this.wait();

}

this.readingReaders++;

} finally {

this.waitingReaders--;

}

}

public synchronized void readUnLock() {

this.readingReaders--;

this.notifyAll();

}

public synchronized void writeLock() throws InterruptedException {

this.waitingWriters++;

try {

while (readingReaders > 0 || writingWriters > 0) {

this.wait();

}

this.writingWriters++;

} finally {

this.waitingWriters--;

}

}

public synchronized void writeUnlock() {

this.writingWriters--;

this.notifyAll();

}

}

public class SharedData {

private final char[] buffer;

private final ReadWriteLock lock = new ReadWriteLock();

public SharedData(int size) {

this.buffer = new char[size];

for (int i = 0; i < size; i++) {

this.buffer[i] = '*';

}

}

public char[] read() throws InterruptedException {

try {

lock.readLock();

return this.doRead();

} finally {

lock.readUnLock();

}

}

public void write(char c) throws InterruptedException {

try {

lock.writeLock();

this.doWrite(c);

} finally {

lock.writeUnlock();

}

}

private void doWrite(char c) {

for (int i = 0; i < buffer.length; i++) {

buffer[i] = c;

slowly(10);

}

}

private char[] doRead() {

char[] newBuf = new char[buffer.length];

for (int i = 0; i < buffer.length; i++) {

newBuf[i] = buffer[i];

}

slowly(50);

return newBuf;

}

private void slowly(int millisecond) {

try {

Thread.sleep(millisecond);

} catch (InterruptedException e) {

e.printStackTrace();

}

}

}

public class WriterWorker extends Thread {

private static final Random random = new Random(System.currentTimeMillis());

private final SharedData data;

private final String filter;

private int indehttp://x = 0;

public WriterWorker(SharedData data, String filter) {

this.data = data;

this.filter = filter;

}

@Override

public void run() {

try {

while (true) {

char c = nextChar();

data.write(c);

Thread.sleep(random.nextInt(1000));

}

} catch (InterruptedException e) {

e.printStackTrace();

}

}

private char nextChar() {

char c = filter.charAt(index);

index++;

if (index >= filter.length())

index = 0;

return c;

}

}

/**

*

* ReadWriteLock

*/

public class ReadWriteLockClient {

public static void main(String[] args) {

final SharedData sharedData = new SharedData(10);

new ReaderWorker(sharedData).start();

new ReaderWorker(sharedData).start();

new ReaderWorker(sharedData).start();

new ReaderWorker(sharedData).start();

new ReaderWorker(sharedData).start();

new WriterWorker(sharedData,"123456").start();

new WriterWorker(sharedData,"abcdef").start();

}

}

结果：

Thread-0 reads **********

Thread-1 reads **********

Thread-2 reads **********

Thread-3 reads **********

Thread-1 reads aaaaaaaaaa

Thread-3 reads aaaaaaaaaa

Thread-0 reads aaaaaaaaaa

Thread-2 reads aaaaaaaaaa

Thread-1 reads aaaaaaaaaa

Thread-2 reads aaaaaaaaaa

Thread-0 reads aaaaaaaaaa

Thread-3 reads aaaaaaaaaa

Thread-1 reads aaaaaaaaaa

Thread-3 reads aaaaaaaaaa

Thread-0 reads aaaaaaaaaa

Thread-2 reads aaaaaaaaaa

Thread-2 reads aaaaaaaaaa

Thread-0 reads aaaaaaaaaa

Thread-1 reads aaaaaaaaaa

Thread-3 reads aaaaaaaaaa

Thread-2 reads aaaaaaaaaa

Thread-0 reads aaaaaaaaaa

Thread-1 reads aaaaaaaaaa

Thread-3 reads aaaaaaaaaa

Thread-0 reads bbbbbbbbbb

Thread-1 reads bbbbbbbbbb

Thread-2 reads bbbbbbbbbb

Thread-3 reads bbbbbbbbbb

Thread-0 reads bbbbbbbbbb

Thread-1 reads bbbbbbbbbb

Thread-3 reads bbbbbbbbbb

Thread-2 reads bbbbbbbbbb

Thread-0 reads bbbbbbbbbb

Thread-1 reads bbbbbbbbbb

Thread-2 reads bbbbbbbbbb

Thread-3 reads bbbbbbbbbb

Thread-0 reads bbbbbbbbbb

Thread-1 reads bbbbbbbbbb

Thread-3 reads bbbbbbbbbb

Thread-2 reads bbbbbbbbbb

Thread-1 reads 3333333333

Thread-2 reads 3333333333

Thread-3 reads 3333333333

...... 省略

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