实现队列_数组队列_1

基于动态数组实现队列
接口

package com.company.queue;

public interface Queue {

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

实现类及测试

package com.company.queue;

import com.company.Array;

/**
 * @program: Array
 * @description: 数组实现队列,先进先出策略
 * @author: Gu
 * @create: 2019-04-14 21:23
 **/

public class ArrayQueue implements Queue{

    private Array array;

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

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

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

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

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

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

    @Override
    public E getFront() {
        return array.get(0);
    }

    @Override
    public String toString() {
        StringBuffer stringBuffer = new StringBuffer();
        stringBuffer.append(String.format("ArrayQueue的size: %d, capacity : %d \n",getSize(), array.length()));
        stringBuffer.append("front [");
        for (int i = 0; i < getSize(); i++) {
            stringBuffer.append(array.get(i));
            if (i == getSize() - 1) {
                stringBuffer.append("] end");
                break;
            }
            stringBuffer.append(",");
        }
        return stringBuffer.toString();
    }

    public static void main(String[] args) {
        ArrayQueue arrayQueue = new ArrayQueue();
        for (int i = 0; i < 10; i++) {
            arrayQueue.enqueue(i);
        }
        System.out.println(arrayQueue);
        System.out.println(arrayQueue.dequeue());
        System.out.println(arrayQueue.getFront());
        System.out.println(arrayQueue);
    }
}

基于数组实现的队列，在出队的时候，时间复杂度为O（n），我们希望是O（1），从而引入第二部分，循环队列。