SimpleObjectFIFO.java Source code

Introduction

Here is the source code for SimpleObjectFIFO.java

Source

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);
    }

    public static void main(String[] args) {
        try {
            SimpleObjectFIFO fifo = new SimpleObjectFIFO(5);
            fifo.printState();

            fifo.add("S01");
            fifo.printState();

            fifo.add("S02");
            fifo.printState();

            fifo.add("S03");
            fifo.printState();

            Object obj = fifo.remove();
            System.out.println("just removed obj=" + obj);
            fifo.printState();

            fifo.add("S04");
            fifo.printState();

            fifo.add("S05");
            fifo.printState();

            fifo.add("S06");
            fifo.printState();
        } catch (InterruptedException x) {
            x.printStackTrace();
        }
    }

}