主要完成任务：
1. read read 并行化 2. read write 不允许 3. write write 不允许
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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(); }
} } } |
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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(); } } } |
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public class WriterWorker extends Thread {
private static final Random random = new Random(System.currentTimeMillis());
private final SharedData data; private final String filter;
private int index = 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; } } |
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/** * * 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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原文链接：https://juejin.cn/post/7021759134072569887
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