Java Queue-数组队列和循环队列-学习记录

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package queue;   import array.Array;   /**  * @Title: ArrayQueue  * @ProjectName Demo03  * @date 2018/9/1214:09  */ public class ArrayQueue<E> implements Queue<E> {     private Array<E> 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.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<String> arrayQueue = new ArrayQueue<>();         arrayQueue.enqueue("1");         arrayQueue.enqueue("2");         System.out.println(arrayQueue);         System.out.println(arrayQueue.getFront());         arrayQueue.dequeue();         System.out.println(arrayQueue);     } }

　

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package queue;   /**  * @Title: LoopQueue  * @ProjectName Demo03  * @date 2018/9/1214:17  */ public class LoopQueue<E> implements Queue<E> {     private E[] data;     // 元素所在位置,元素入队下一个位置     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);     }       @Override     public int getSize() {         return size;     }       @Override     public boolean isEmpty() {         return front == tail;     }       public int getCapacity() {         return data.length - 1;     }       @Override     public void enqueue(E e) {         if ((tail + 1) % data.length == front) {             // 队列已满             resize(getCapacity() * 2);         }         data[tail] = e;         tail = (tail + 1) % data.length;         size++;     }       @Override     public E dequeue() {         if (isEmpty()) {             throw new IllegalArgumentException("队列为空");         }         E e = data[front];         front = (front + 1) % data.length;         size--;         if (size == getCapacity() / 4 && getCapacity() / 2 != 0) {             resize(getCapacity() / 2);         }         return e;     }       @Override     public E getFront() {         if (isEmpty()) {             throw new IllegalArgumentException("队列为空");         }         return data[front];     }       private void resize(int capacity) {         E[] newData = (E[]) new Object[capacity + 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("LoopQueue: 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);             }         }     } }