package threadbook.ch18;

public class SimpleObjectFIFO extends Object {

private Object[] queue;

private int capacity;

private int size;

private int head;

private int tail;

public SimpleObjectFIFO(int cap) {

capacity = ( cap > 0 ) ? cap : 1; // at least 1

queue = new Object[capacity];

head = 0;

tail = 0;

size = 0;

}

public synchronized int getSize() {

return size;

}

public synchronized boolean isFull() {

return ( size == capacity );

}

public synchronized void add(Object obj) throws InterruptedException {

while ( isFull() ) {

wait();

}

queue[head] = obj;

head = ( head + 1 ) % capacity;

size++;

notifyAll(); // let any waiting threads know about change

}

public synchronized Object remove() throws InterruptedException {

while ( size == 0 ) {

wait();

}

Object obj = queue[tail];

queue[tail] = null; // don't block GC by keeping unnecessary reference

tail = ( tail + 1 ) % capacity;

size--;

notifyAll(); // let any waiting threads know about change

return obj;

}

public synchronized void printState() {

StringBuffer sb = new StringBuffer();

sb.append("SimpleObjectFIFO:\n");

sb.append(" capacity=" + capacity + "\n");

sb.append(" size=" + size);

if ( isFull() ) {

sb.append(" - FULL");

} else if ( size == 0 ) {

sb.append(" - EMPTY");

}

sb.append("\n");

sb.append(" head=" + head + "\n");

sb.append(" tail=" + tail + "\n");

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

sb.append(" queue[" + i + "]=" + queue[i] + "\n");

}

System.out.print(sb);

}

}