数据结构-循环队列

package org.butupi.queue;

import java.util.Scanner;

//循环队列实现
class CircleArrayQueue {
	private int[] arr;
	private int rear;// end
	private int front;// begin
	private int size;
	private final int limit;	//队列最大容量
	
	public CircleArrayQueue(int limit) {
		arr = new int[limit];
		rear = 0;
		front = 0;
		size = 0;
		this.limit = limit;
	}
	
	//add
	public void push(int value) {
		if (this.isFull()) {
			throw new RuntimeException("队列满了，不能再加了");
		}
		size++;
		arr[rear] = value;
		rear = nextIndex(rear);
	}

	//remove
	public int pop() {
		if (this.isEmpty()) {
			throw new RuntimeException("队列空了，不能再拿了");
		}
		size--;
		int ans = arr[front];
		front = nextIndex(front);
		return ans;
	}

	public boolean isEmpty() {
		return size == 0;
	}
	
	public boolean isFull() {
		return size == limit;
	}

	// 如果现在的下标是i，返回下一个位置（关键点）代替了取模的思想
	private int nextIndex(int i) {
		return i < limit - 1 ? i + 1 : 0;
	}
	
	public int peek() {
		return arr[front];
	}
	
	public void showQueue() {
		if (this.isEmpty()) {
			System.out.println("队列空");
			return;
		}
		int tmpSize = size;
		for(int i = front;tmpSize>0;i = nextIndex(i),tmpSize--) {
			System.out.println(arr[i]);
			
		}
	}
}


// for test
public class RingArrayDemo {
	public static void main(String[] args) {
		CircleArrayQueue arrayQueue = new CircleArrayQueue(5);

		char key = ' ';
		Scanner scanner = new Scanner(System.in);
		boolean loop = true;
		while (loop) {
			System.out.println("s(show):显示队列");
			System.out.println("e(exit):退出程序");
			System.out.println("a(add):添加数据到队列");
			System.out.println("g(get):从队列取出数据");
			System.out.println("h(head):显示队列头");
			System.out.print("请输入：");
			key = scanner.next().charAt(0);// 接受一个字符

			switch (key) {
			case 's':
				arrayQueue.showQueue();
				break;
			case 'a':
				System.out.println("请输入一个数：");
				int value = scanner.nextInt();
				arrayQueue.push(value);
				break;
			case 'g':
				try {
					int res = arrayQueue.pop();
					System.out.printf("取出的数据是%dn", res);
				} catch (Exception e) {
					System.out.println(e.getMessage());
				}
				break;
			case 'h':
				try {
					int head = arrayQueue.peek();
					System.out.printf("队列头的数据是%dn", head);
				} catch (Exception e) {
					System.out.println(e.getMessage());
				}
				break;
			case 'e':
				scanner.close();
				loop = false;
				break;
			default:
				break;
			}
		}
		System.out.println("程序退出!");
	}
}