队列（一）——非循环（Java版）

非循环队列

• 判空： front == rear
• 判满：rear == maxsize - 1
• 队列元素个数：rear - front
• front指针移动方式：front = front +1
• rear指针移动方式：rear = rear +1

import java.awt.Font;
import java.util.Scanner;
import javax.management.RuntimeErrorException;

public class ArrayQueueDemo {

	public static void main(String[] args) {
		//创建队列
		ArrayQueue arrayQueue = new ArrayQueue(3);
		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):查看队列头的数据");
			key = scanner.next().charAt(0);
			switch (key) {
			case 's':
				arrayQueue.showQueue();
				break;
			case 'e':
				arrayQueue.showQueue();
				break;
			case 'a':
				System.out.println("输入一个数");
				int value = scanner.nextInt();
				arrayQueue.addQueue(value);
				break;
			case 'g':
				try {
					int res = arrayQueue.getQueue();
					System.out.printf("取出的数据是%d\n",res);
				}catch (Exception e) {
					System.out.println(e.getMessage());
				}
				break;
			case 'h':
				try {
					int res = arrayQueue.headQueue();
					System.out.printf("队列头的数据是%d\n",res);
				}catch (Exception e) {
					System.out.println(e.getMessage());

				}
				break;
			

			default:
				scanner.close();
				loop = false;
				break;
			}
		}
		System.out.println("程序退出");

	}

} 
//队列
class ArrayQueue{
	private int maxsize;
	private int front;
	private int rear;
	private int[] arr;
	//构造器
	public ArrayQueue(int arrmaxsize) {
		maxsize = arrmaxsize;
		front = -1;
		rear = -1;
		arr = new int[maxsize];
	}
	//判满
	public boolean isFull() {
		return rear == maxsize - 1;
	}
	//判空
	public boolean isEmpty() {
		return rear == front;
	}
	//入队
	public void addQueue(int n) {
		if(isFull()) {
			System.out.println("队列已满，不能再添加！");
			return;
		}
		rear++;
		arr[rear] = n;
	}
	//出队
	public int getQueue() {
		if(isEmpty()) {
			throw new RuntimeException("队列为空，不可取出元素！");
		}
		front++;
		return arr[front];
	}
	//遍历
	public void showQueue() {
		if(isEmpty()) {
			System.out.println("队列为空!");
			return;
		}
		for(int i=0;i<arr.length;i++) {
			System.out.printf("arr[%d]=%d\n",i,arr[i]);
		}
	}
	//显示队头元素
	public int headQueue() {
		if(isEmpty()) {
			throw new RuntimeException("队列为空，不可取出元素！");
		}
		return arr[front+1];
	}
}

结果示意图