IntRingBuffer

package mt3.util;
/*************************************************************************
 *  Compilation:  javac RingBuffer.java
 *  Execution:    java RingBuffer
 *
 *  Ring buffer (fixed size queue) implementation using a circular array
 *  (array with wrap-around).
 *
 *  Copyright (c) 2007, Robert Sedgewick and Kevin Wayne.
 *  Edited by Chris Dennett (C.R.Dennett@2006.ljmu.ac.uk)
 *
 *************************************************************************/


// suppress unchecked warnings in Java 1.5.0_6 and later
@SuppressWarnings("unchecked")

public class IntRingBuffer {
    private int[] a;             // queue elements
    private int N = 0;           // number of elements on queue
    private int first = 0;       // index of first element of queue
    private int last  = 0;       // index of next available slot

    private int iter_i = 0;


    // cast needed since no generic array creation in Java
    public IntRingBuffer(int capacity) {
        a = new int[capacity];
        for (int i = 0; i < capacity; i++) {
            a[i] = Integer.MIN_VALUE;
        }
    }

    public boolean isEmpty() { return N == 0; }
    public int size()        { return N;      }

    public void enqueue(int item) {
        if (N == a.length) { throw new RuntimeException("Ring buffer overflow"); }
        a[last] = item;
        last = (last + 1) % a.length;     // wrap-around
        N++;
    }

    // remove the least recently added item - doesn't check for underflow
    public int dequeue() {
        if (isEmpty()) { throw new RuntimeException("Ring buffer underflow"); }
        int item = a[first];
        a[first] = Integer.MIN_VALUE;                  // to help with garbage collection
        N--;
        first = (first + 1) % a.length;   // wrap-around
        return item;
    }

    public void iter_reset() {
        iter_i = 0;
    }

    public boolean contains(final int n) {
        iter_reset();
        int i = 0;
        while ((i = iter_next()) != Integer.MIN_VALUE) {
            if (i == n) return true;
        }
        return false;
    }

    public int iter_next() {
        if (!iter_hasNext()) return Integer.MIN_VALUE;
        return a[iter_i++];
    }

    public boolean iter_hasNext() {
        return iter_i < N;
    }
}