数据结构（java）之数组队列和循环队列的比较

在main方法中，通过Queue接口分别调用数组队列和循环队列的方法，进行入队和出队操作，比较从开始入队到结束出队所用的时间

import java.util.Random;

public class Main {

    private static double testQueue(Queue<Integer> q,int opCount){
        Long startTime = System.nanoTime();//记录开始入队时间
        Random random = new Random();
        for (int i=0;i<opCount;i++)
            q.enqueue(random.nextInt(Integer.MAX_VALUE)); //入队操作
        for (int i=0;i<opCount;i++);
            q.dequeue();   //出队操作
        Long endTime = System.nanoTime();  //记录出队结束时间
        double time = (endTime-startTime)/1000000000.0;
        return time;
    }
    public static void main(String[] args) {
	// write your code here
        int opCount = 100000;
        //数组队列用时
        ArrayQueue<Integer> arrayQueue = new ArrayQueue<>();
        double time1 = testQueue(arrayQueue,opCount);
        System.out.println("ArrayQueue: time"+time1+'s');
        //循环队列用时
        LoopQueue<Integer> loopQueue = new LoopQueue<>();
        double time2 = testQueue(loopQueue,opCount);
        System.out.println("LoopQueue: time"+time2+'s');
    }
}

Queue接口

public interface Queue<E> {

    int getSize();
    boolean isEmpty();
    void enqueue(E e);
    E dequeue();
    E getFront();
}

数组队列操作

public class ArrayQueue<E> implements Queue<E> {

    private Array<E> array;

    public ArrayQueue(int capacity){
        array = new Array<>(capacity);
    }

    public ArrayQueue(){
        array = new Array<>();
    }

    @Override
    public int getSize(){
        return array.getSize();
    }

    @Override
    public boolean isEmpty(){
        return array.isEmpty();
    }

    public int getCapacity(){
        return array.getCapacity();
    }

    @Override
    public void enqueue(E e){
        array.addLast(e);
    }

    @Override
    public E dequeue(){
        return array.removeFirst();
    }

    @Override
    public E getFront(){
        return array.getFirst();
    }

    @Override
    public String toString(){

        StringBuilder res = new StringBuilder();
        res.append("Queue: ");
        res.append("front [");
        for(int i = 0 ; i < array.getSize() ; i ++){
            res.append(array.get(i));
            if(i != array.getSize() - 1)
                res.append(", ");
        }
        res.append("] tail");
        return res.toString();
    }

    public static void main(String[] args){

        ArrayQueue<Integer> queue = new ArrayQueue<>();
        for(int i = 0 ; i < 10 ; i ++){
            queue.enqueue(i);
            System.out.println(queue);

            if(i % 3 == 2){
                queue.dequeue();
                System.out.println(queue);
            }
        }
    }
}

循环队列操作

public class LoopQueue<E> implements Queue<E> {

    private E[] data;
    private int front, tail;
    private int size;
    
    public LoopQueue(int capacity){
        data = (E[])new Object[capacity + 1];
        front = 0;
        tail = 0;
        size = 0;
    }

    public LoopQueue(){
        this(10);
    }

    public int getCapacity(){
        return data.length - 1;
    }

    @Override
    public boolean isEmpty(){
        return front == tail;
    }

    @Override
    public int getSize(){
        return size;
    }

    @Override
    public void enqueue(E e){

        if((tail + 1) % data.length == front)
            resize(getCapacity() * 2);

        data[tail] = e;
        tail = (tail + 1) % data.length;
        size ++;
    }

    @Override
    public E dequeue(){

        if(isEmpty())
            throw new IllegalArgumentException("Cannot dequeue from an empty queue.");

        E ret = data[front];
        data[front] = null;
        front = (front + 1) % data.length;
        size --;
        if(size == getCapacity() / 4 && getCapacity() / 2 != 0)
            resize(getCapacity() / 2);
        return ret;
    }

    @Override
    public E getFront(){
        if(isEmpty())
            throw new IllegalArgumentException("Queue is empty.");
        return data[front];
    }

    private void resize(int newCapacity){

        E[] newData = (E[])new Object[newCapacity + 1];
        for(int i = 0 ; i < size ; i ++)
            newData[i] = data[(i + front) % data.length];

        data = newData;
        front = 0;
        tail = size;
    }

    @Override
    public String toString(){

        StringBuilder res = new StringBuilder();
        res.append(String.format("Queue: size = %d , capacity = %d\n", size, getCapacity()));
        res.append("front [");
        for(int i = front ; i != tail ; i = (i + 1) % data.length){
            res.append(data[i]);
            if((i + 1) % data.length != tail)
                res.append(", ");
        }
        res.append("] tail");
        return res.toString();
    }

    public static void main(String[] args){

        LoopQueue<Integer> queue = new LoopQueue<>(5);
        for(int i = 0 ; i < 10 ; i ++){
            queue.enqueue(i);
            System.out.println(queue);

            if(i % 3 == 2){
                queue.dequeue();
                System.out.println(queue);
            }
        }
    }
}