EvictingQueue.java

package jaci.openrio.toast.lib;

import java.lang.reflect.Array;

/**
 * A Queue that will evict the oldest element when a new one is added
 *
 * @author Jaci
 */
public class EvictingQueue<T> {

    Object[] array;
    int size;

    /**
     * Create a new FIFO buffer.
     * @param i The size of the array
     */
    public EvictingQueue(int i) {
        this.size = i;
        array = new Object[size];
    }

    /**
     * Add a new value to the array
     */
    public void add(T value) {
        pushBack();
        array[0] = value;
    }

    /**
     * Clear the array
     */
    public void clear() {
        array = new Object[size];
    }

    /**
     * Push values back
     */
    void pushBack() {

        for (int i = array.length - 1; i > 0; i--) {
            if (array[i - 1] != null) {
                array[i] = null;
                array[i] = array[i - 1];
            }
        }
        array[0] = null;
    }

    /**
     * Get the contents of the array
     * @param contents A 'base' array to convert to. <i> e.g. new String[0]; </i>
     * @return The array
     */
    public T[] toArray(T[] contents) {
        int s = size;
        if (contents.length < s) {
            @SuppressWarnings("unchecked") T[] newArray
                    = (T[]) Array.newInstance(contents.getClass().getComponentType(), s);
            contents = newArray;
        }
        System.arraycopy(this.array, 0, contents, 0, s);
        if (contents.length > s) {
            contents[s] = null;
        }
        return contents;
    }

}