栈和队列（队列）

 

interface Queue01<E>

interface Queue01<E>{

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

class Array01<E>

class Array01<E> {

    private E[] data;
    private int size;

    // 构造函数，传入数组的容量capacity构造Array01
    public Array01(int capacity){
        data = (E[])new Object[capacity];
        size = 0;
       
    }
     
    // 无参数的构造函数，默认数组的容量capacity=20
    public Array01(){
        this(20);
    }

    // 获取数组的容量
    public int getCapacity(){
        return data.length;
    }

    // 获取数组中的元素个数
    public int getSize(){
        return size;   
    }

    // 返回数组是否为空
    public boolean isEmpty(){
        return 0 == size;   
    }

    // 在index索引的位置插入一个新元素e
    public void add(int index, E e){
        if(index < 0 || index > size){
            System.out.printf("index = %d\n",index);
            throw new IllegalArgumentException("Add failed. Index is illegal.");
        }

        if(data.length == size){
            resize(2 * data.length);
        }

        for(int i = size - 1; i >= index; i--){
            data[i + 1] = data[i];
        }

        data[index] = e;
        size++;
       
    }

    // 向所有元素后添加一个新元素
    public void addLast(E e){
        add(size,e);
    }

    // 在所有元素前添加一个新元素
    public void addFirst(E e){
        add(0,e);
    }

    // 获取index索引位置的元素
    public E get(int index){
        if(index < 0 || index >= size){
            throw new IllegalArgumentException("Get failed. Index is illegal.");
        }

        return data[index];
    }

    public E getLast(){
        return get(size - 1);
    }

    public E getFirst(){
        return get(0);
    }

    // 修改index索引位置的元素为e
    public void set(int index, E e){
        if(index < 0 || index >= size){
            throw new IllegalArgumentException("Set failed. Index is illegal.");
        }

        data[index] = e;
    }

    // 查找数组中是否有元素e
    public boolean contains(E e){
        /*for(int i = 0; i < size; i++){
            if(data[i].equals(e)){
                return true;
            }
        }*/
        if(-1 != find(e)){
            return true;
        }

        return false;
    }

    // 查找数组中元素e所在的索引，如果不存在元素e，则返回-1
    public int find(E e){
        for(int i = 0; i < size; i++){
            if(data[i].equals(e)){
                return i;
            }
        }

        return -1;
    }

    // 从数组中删除index位置的元素, 返回删除的元素
    public E remove(int index){
        if(index < 0 || index >= size){
            throw new IllegalArgumentException("Remove failed. Index is illegal.");
        }

        E res = data[index];
        for(int i = index + 1; i < size; i++){
            data[i - 1] = data[i];
        }

        data[size - 1] = null;
        size--;
        
        if(data.length / 4 == size && data.length / 2 != 0){
            resize(2 * data.length);
        }
        return res;
    }

    // 从数组中删除第一个元素, 返回删除的元素
    public E removeFirst(){
        return remove(0);
    }

    // 从数组中删除最后一个元素, 返回删除的元素
    public E removeLast(){
        return remove(size - 1);
    }

    // 从数组中删除元素e
    public void removeElement(E e){
       int index = find(e);

       if(-1 != index){
            remove(index);
       }else{
            throw new IllegalArgumentException("Remove failed. The element is not exsit.");
        }
    }

    @Override
    public String toString(){
        StringBuilder res = new StringBuilder();
        res.append(String.format("Array01: size = %d, capacity = %d\n",size,data.length));
        res.append('[');
        for(int i = 0; i < size; i++){
            res.append(data[i]);
            if(size - 1 != i){
                res.append(", ");
            }
        }

        res.append(']');

        return res.toString();
    }

    // 将数组空间的容量变成newCapacity大小
    private void resize(int newCapacity){
        E[] newData = (E[])new Object[newCapacity];

        for(int i = 0; i < size; i++){
            newData[i] = data[i];
        }

        data = newData;
        
    }

}

public class ArrayQueue01<E> implements Queue01<E>

public class ArrayQueue01<E> implements Queue01<E>{

    private Array01<E> array;

    public ArrayQueue01(int capacity){
        array = new Array01<>(capacity);
    }

    public ArrayQueue01(){
        array = new Array01<>();
    }

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

    @Override
    public boolean isEmpty(){
       return 0 == array.getSize();
    }

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

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

    @Override
    public E dequeue(){
        if(isEmpty()){
            throw new IllegalArgumentException("Dequeue failed. The queue is empty.");
        }

        return    array.removeFirst();
    }

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

    @Override
    public String toString(){
        StringBuilder res = new StringBuilder();
        res.append(String.format("ArrayQueue01: size = %d, capacity = %d\n",array.getSize(),array.getCapacity()));
        res.append("Front [");
        for(int i = 0; i < array.getSize(); i++){
            res.append(array.get(i));
            if(array.getSize() - 1 != i){
                res.append(", ");
            }
        }

        res.append("] Tail");
        
        return res.toString();

    }

    public static void main(String[] args) {

        ArrayQueue01<Integer> queue = new ArrayQueue01<>();
        for(int i = 0 ; i < 8 ; i ++){
            queue.enqueue(i);
            System.out.println(queue);
            if(i % 3 == 2){
                queue.dequeue();
                System.out.println(queue);
            }
        }
    }
}

 

运行结果：