增加淘宝群内容，修改部分文件组织

数据结构(双语)/数据结构 day16【瑞客论坛 www.ruike1.com】/代码/05-队列/src/com/mj/circle/CircleQueue.java

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+package com.mj.circle;
+
+@SuppressWarnings("unchecked")
+public class CircleQueue<E> {
+	private int front;
+	private int size;
+	private E[] elements;
+	private static final int DEFAULT_CAPACITY = 10;
+	
+	public CircleQueue() {
+		elements = (E[]) new Object[DEFAULT_CAPACITY];
+	}
+	
+	public int size() {
+		return size;
+	}
+
+	public boolean isEmpty() {
+		return size == 0;
+	}
+	
+	public void clear() {
+		for (int i = 0; i < size; i++) {
+			elements[index(i)] = null;
+		}
+		front = 0;
+		size = 0;
+	}
+
+	public void enQueue(E element) {
+		ensureCapacity(size + 1);
+		
+		elements[index(size)] = element;
+		size++;
+	}
+
+	public E deQueue() {
+		E frontElement = elements[front];
+		elements[front] = null;
+		front = index(1);
+		size--;
+		return frontElement;
+	}
+
+	public E front() {
+		return elements[front];
+	}
+	
+	@Override
+	public String toString() {
+		StringBuilder string = new StringBuilder();
+		string.append("capcacity=").append(elements.length)
+		.append(" size=").append(size)
+		.append(" front=").append(front)
+		.append(", [");
+		for (int i = 0; i < elements.length; i++) {
+			if (i != 0) {
+				string.append(", ");
+			}
+			
+			string.append(elements[i]);
+		}
+		string.append("]");
+		return string.toString();
+	}
+	
+	private int index(int index) {
+		index += front;
+		return index - (index >= elements.length ? elements.length : 0);
+	}
+	
+	/**
+	 * 保证要有capacity的容量
+	 * @param capacity
+	 */
+	private void ensureCapacity(int capacity) {
+		int oldCapacity = elements.length;
+		if (oldCapacity >= capacity) return;
+		
+		// 新容量为旧容量的1.5倍
+		int newCapacity = oldCapacity + (oldCapacity >> 1);
+		E[] newElements = (E[]) new Object[newCapacity];
+		for (int i = 0; i < size; i++) {
+			newElements[i] = elements[index(i)];
+		}
+		elements = newElements;
+		
+		// 重置front
+		front = 0;
+	}
+}