通用队列数组大小调整

import java.util.Arrays;
/* from 
时   代    Java - nowjava.com*/


public class GenericQueueArrayResize<Item> {

    private int first;

    private int numelements;

    private Object[] data;


    public GenericQueueArrayResize() {

        data = new Object[1];

        first = 0;

        numelements = 0;

    }/** 来 自 NowJava.com - 时代Java**/


    private void resize(int newsize) {

        System.out.println(String.format("Resizing array to %d", newsize));

        // resize the array

        Object[] newdata = new Object[newsize];

        for (int i = 0; i < numelements; i++) {

            newdata[i] = data[(first + i) % data.length];

            data[i] = null; // is this necessary?

        }

        first = 0;

        data = newdata; // or does this make all of data go out of scope?

    }


    public Item dequeue() {

        if (numelements == 0) {

            throw new java.util.NoSuchElementException();

        }

        Item firstval = (Item) data[first];

        data[first] = null;

        numelements -= 1;

        // check if this is the last item

        if (numelements == 0)

            first = 0;

        else {

            first = (first + 1) % data.length;

            if (numelements <= data.length / 4)

                resize(data.length / 2);

        }

        return firstval;

    }


    public void enqueue(Item s) {

        // check if array is full

        if (numelements >= data.length)

            resize(data.length * 2);

        data[(first + numelements) % data.length] = s;

        numelements += 1;

    }


    public static void main(String[] args) {

        GenericQueueArrayResize<Integer> queue = new GenericQueueArrayResize<Integer>();

        int N = Integer.parseInt(args[0]);

        double prob = Double.parseDouble(args[1]);

        // testing enqueue-dequeue

        System.out.println("********** Testing Enqueue-Dequeue **********");

        for (int i = 0; i < N; i++) {

            if (StdRandom.uniform() < prob) {

                try {

                    queue.enqueue(1);

                } catch (java.lang.