Sinkronisasi dalam Java

public synchronized void enter(Object item){
    while (count == BUFFER_SIZE)
    Thread.yeild();
    ++count;
    buffer[in] = item;
    in = (in+1) % BUFFER_SIZE;
}

public synchronized void remove (){
    Object item;
    while (count == 0)
    Thread.yeild();
    --count;
    item = buffer[out]
    out = (out+1) % BUFFER_SIZE;
    return item
}