算法导论示例-Queue

/**
 * Introduction to Algorithms, Second Edition 
 * 10.1 Queues
 * @author 土豆爸爸
 * 
 */
public class Queue {
    int[] array;
    int head; //队列头索引
    int tail; //队列尾索引
    
    public Queue(int size) {
        array = new int[size];        
    }
    
    /**
     * 将元素x添加到队列。队列的尾索引加1。
     * @param x 待添加的元素
     */
    public void enqueue(int x) {
        if(head == (tail + 1) % array.length) {
            throw new RuntimeException("Over flow");
        }
        array[tail] = x;
        //尾索引加1，并自动折转
        tail = (tail + 1) % array.length; 
    }
    
    /**
     * 从队列从返回头元素。队列的头索引加1。
     * @return 队列头元素
     */
    public int dequeue() {
        if(head == tail) {
            throw new RuntimeException("Under flow");            
        }
        int result = array[head];
        //头索引加1，并自动折
        head = (head + 1) % array.length;
        return result;
    }
}

import junit.framework.TestCase;

public class QueueTest extends TestCase {
    public void testStack() {
        Queue q = new Queue(10);
        q.enqueue(1);
        q.enqueue(2);
        q.enqueue(3);
        assertEquals(1, q.dequeue());
        assertEquals(2, q.dequeue());
        q.enqueue(4);
        q.enqueue(5);
        assertEquals(3, q.dequeue());
        assertEquals(4, q.dequeue());
        assertEquals(5, q.dequeue());
        
        try{
            q.dequeue();
            fail("dequeue应抛出异常");
        } catch(Exception e) {
            assertTrue(e.getMessage().equals("Under flow"));
        }
    }
}