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
