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| import java.util.Random;
class Data {
private final char[] buffer;
private final ReadWriteLock lock = new ReadWriteLock();
Data(int size) {
this.buffer = new char[size];
for(int i = 0; i < size; i++) {
buffer[i] = '*';
}
}
char[] read() throws InterruptedException {
lock.readLock();
try {
return doRead();
} finally {
lock.readUnlock();
}
}
void write(char c) throws InterruptedException {
lock.writeLock();
try {
doWrite(c);
} finally {
lock.writeUnlock();
}
}
private char[] doRead() {
char[] newBuffer = new char[buffer.length];
System.arraycopy(buffer, 0, newBuffer, 0, newBuffer.length);
slowly();
return newBuffer;
}
private void doWrite(char c) {
for(int i = 0; i < buffer.length; i++) {
buffer[i] = c;
slowly();
}
}
private void slowly() {
try {
Thread.sleep(50);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
class WriterThread extends Thread {
private static final Random random = new Random();
private final Data data;
private final String filler;
private int index = 0;
WriterThread(Data data, String filler) {
this.data = data;
this.filler = filler;
}
@Override
public void run() {
try {
while(true) {
char c = nextChar();
data.write(c);
Thread.sleep(random.nextInt(3000));
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
private char nextChar() {
if(index >= filler.length()) {
index = 0;
}
char c = filler.charAt(index);
index++;
return c;
}
}
class ReaderThread extends Thread {
private final Data data;
ReaderThread(Data data) {
this.data = data;
}
@Override
public void run() {
try {
while(true) {
char[] readBuffer = data.read();
System.out.println(Thread.currentThread().getName() + " read " + String.valueOf(readBuffer));
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
class ReadWriteLock {
private int readingReaders = 0;
private int waitingWriters = 0;
private int writingWriters = 0;
private boolean preferWriter = true;
synchronized void readLock() throws InterruptedException {
while(writingWriters > 0 || (preferWriter && waitingWriters > 0)) {
wait();
}
readingReaders++;
}
synchronized void readUnlock() {
readingReaders--;
preferWriter = true;
notifyAll();
}
synchronized void writeLock() throws InterruptedException{
waitingWriters++;
try {
while(readingReaders > 0 || writingWriters > 0) {
wait();
}
} finally {
waitingWriters--;
}
writingWriters++;
}
synchronized void writeUnlock() {
writingWriters--;
preferWriter = false;
notifyAll();
}
}
public class Test {
public static void main(String[] args) {
var data = new Data(10);
new ReaderThread(data).start();
new ReaderThread(data).start();
new ReaderThread(data).start();
new ReaderThread(data).start();
new ReaderThread(data).start();
new ReaderThread(data).start();
new WriterThread(data, "ABCDEF").start();
new WriterThread(data, "abcdef").start();
}
}
|