package DataStructures;
public
class QueueArray
{
static final int DEFAULT_CAPACITY = 10; private Object[] theArray; private int currentSize; private int front; private int back;
/** * Construct the queue. * 
*/ public QueueArray() { this(DEFAULT_CAPACITY); } /** * Construct the queue. * * @param capacity */ public QueueArray(int capacity) { theArray = new Object[capacity]; MakeEmpty(); } /** * Make the queue logically empty. * */ public void MakeEmpty() { currentSize = 0; front = 0; back = -1; } public boolean IsEmpty() { return currentSize == 0; } public boolean IsFull() { return currentSize == theArray.length; } /** * Get the least recently inserted item in the queue. Does not alter the * queue. * * @return the least recently inserted item in the queue, or null, if empty. */ public Object getFront() { if (IsEmpty()) return null; return theArray[front]; } /** * Insert a new item into the queue. * * @param x * the item to insert. * @throws Overflow * if queue is full. */ public void Enqueue(Object x) throws Overflow { if (IsFull()) throw new Overflow(); back = increment(back); theArray[back] = x; currentSize++; } /** * Internal method to increment with wraparound. * * @param x * any index in theArray`s range. * @return x+1,or 0,if x is at the end of theArray; */ private int increment(int x) { if (++x == theArray.length) x = 0; return x; } /** * Return and remove the least recently inserted item from the queue. * * @return the least recently inserted item, or null, if empty. */ public Object Dequeue() { if (IsEmpty()) return null; currentSize--; Object frontItem = theArray[front]; theArray[front] = null; front = increment(front); return frontItem; }
}
本文转自冬冬博客园博客，原文链接：http://www.cnblogs.com/yuandong/archive/2006/09/11/500814.html
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