1.数组队列

数组实现单队列

package com.zhiyang.queuearr;

import java.util.Scanner;

import javax.swing.text.AbstractDocument.BranchElement;

public class arrqueue {
    public static void main(String[] args) {
        //创建一个对象
        ArrayQueue arrayQueue=new ArrayQueue(3);
        char key=' ';//接收用户输入
        Scanner scanner=new Scanner(System.in);
        boolean loop=true;
        while(loop) {
            System.out.println("s:展示队列数据");
            System.out.println("e:退出");
            System.out.println("a:添加数据");
            System.out.println("g:取数据");
            System.out.println("h:查看队头数据");
            key=scanner.next().charAt(0);
            switch (key) {
            case 's':
                arrayQueue.showQueue();
                break;
            case 'a':
                System.out.println("请输入一个数字\n");
                int value=scanner.nextInt();
                
                arrayQueue.addQueue(value);
                break;
                
            case 'g':
                try {
                    int res=arrayQueue.getQueue();
                    System.out.printf("出队的为：%d\n",res);
                    
                } catch (Exception e) {
                    // TODO: handle exception
                    System.out.println(e.getMessage());
                    
                }
                break;
            
            case 'h':
                try {
                    int res=arrayQueue.headQueue();
                    System.out.printf("队列头为：%d\n",res);
                } catch (Exception e) {
                    // TODO: handle exception
                    System.out.println(e.getMessage());
                    
                }
                break;
            case 'e':
                scanner.close();
                loop=false;
                break;

            default:
                break;
            }
            
            
        }
        System.out.println("程序退出");
    }

}

//使用数组模拟队列-编写一个arr-queue的队列
class ArrayQueue {
    private int maxSize;
    private int front;// queue的头
    private int rear;// queue的尾
    private int[] arr;

    public ArrayQueue(int arrMaxsize) {
        maxSize = arrMaxsize;
        arr = new int[maxSize];
        front = -1;//指向队列头的前一个位置，当插入一个元素时，刚好
        rear = -1;

    }
    //判断队列是否满
    public boolean isFull() {
        return rear==maxSize-1;
        
    }
    //判断队列是否空
    public boolean isEmpty() {
        return rear==front;
        
        
    }
    //添加数据
    public void addQueue(int n) {
        if(isFull()) {
            System.out.println("Queue is full");
            return;
        }
        rear++;
        arr[rear]=n;
    }
    //元素出队
    public int getQueue() {
        if(isEmpty()) {
            throw new RuntimeException("Queue is empty");
        }
        front++;
        System.out.printf("运行此处");
        return arr[front];
        
    }
    //显示队列的所有数据
    public void showQueue() {
        if(isEmpty()) {
            System.out.println("Queue is empty");   
        }
        for(int i=0;i<arr.length;i++) {
            System.out.printf("arr[%d]=%d\n",i,arr[i]);
        }
        
    }
    //显示头结点
    public int  headQueue() {
        if(isEmpty()) {
            throw new  RuntimeException("Queue is empty");
            
        }
        return arr[front+1];
        
    }
    
}

数组实现循环队列

import java.util.Scanner;
public class CircleArrayQueue {
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        //创建一个对象
                CircleArrQueue arrayQueue=new CircleArrQueue(4);//最大元素为3
                char key=' ';//接收用户输入
                Scanner scanner=new Scanner(System.in);
                boolean loop=true;
                while(loop) {
                    System.out.println("s:展示队列数据");
                    System.out.println("e:退出");
                    System.out.println("a:添加数据");
                    System.out.println("g:取数据");
                    System.out.println("h:查看队头数据");
                    key=scanner.next().charAt(0);
                    switch (key) {
                    case 's':
                        arrayQueue.showQueue();
                        break;
                    case 'a':
                        System.out.println("请输入一个数字\n");
                        int value=scanner.nextInt();
                        
                        arrayQueue.addQueue(value);
                        break;
                        
                    case 'g':
                        try {
                            int res=arrayQueue.getQueue();
                            System.out.printf("出队的为：%d\n",res);
                            
                        } catch (Exception e) {
                            // TODO: handle exception
                            System.out.println(e.getMessage());
                            
                        }
                        break;
                    
                    case 'h':
                        try {
                            int res=arrayQueue.headQueue();
                            System.out.printf("队列头为：%d\n",res);
                        } catch (Exception e) {
                            // TODO: handle exception
                            System.out.println(e.getMessage());
                            
                        }
                        break;
                    case 'e':
                        scanner.close();
                        loop=false;
                        break;

                    default:
                        break;
                    }
                    
                    
                }
                System.out.println("程序退出");

    }

}

class CircleArrQueue {
    private int maxSize;
    private int front;// queue的头，指向队列第一个元素
    private int rear;// queue的尾，指向队列最后元素的下一个元素
    private int[] arr;

    public CircleArrQueue(int arrMaxSize) {
        maxSize = arrMaxSize;
        arr = new int[maxSize];

    }

    // 判断队列是否已满
    public boolean isFull() {
        return (rear + 1) % maxSize == front;

    }

    // 判断队列是否为空
    public boolean isEmpty() {
        return rear == front;
    }

    // 添加数据
    public void addQueue(int n) {
        // 判断队列是否已满
        if (isFull()) {
            System.out.println("Queue is full");
            return;
        }
        // 直接将数据加入
        arr[rear] = n;
        // rear后移取模
        rear = (rear + 1) % maxSize;
    }

    // 元素出队
    public int getQueue() {
        if (isEmpty()) {
            throw new RuntimeException("Queue is empty");
        }
        // front指向队列第一个元素
        // 1.先将取出的数据保存
        // 2.然后重新设置front的值，此处之所以不考虑直接使用front-1来取值，
        // 是考虑到front可能会取模，此时会产生数组越界的错误
        // 3.将取出的值返回

        int value = arr[front];
        front = (front + 1) % maxSize;
        return value;

    }

    // 显示队列的所有数据
    public void showQueue() {
        if (isEmpty()) {
            System.out.println("Queue is empty");
            return;
        }
        for (int i = front; i <front+size(); i++) {
            //当所取元素在front后时，i是小于maxsize的，此时数组不越界
            //但当元素在front前时，需要取模来避免数组越界
            System.out.printf("arr[%d]=%d\n", i, arr[i%maxSize]);
        }

    }
    //显示当前队列有效数据的个数
    public int size() {
        return (rear-front+maxSize)%maxSize;
        
    }
    
    //显示头结点
        public int  headQueue() {
            if(isEmpty()) {
                throw new  RuntimeException("Queue is empty");
                
            }
            return arr[front];
            
        }

}