Question

我正在用Java做一个项目，我需要创建一个队列方法。

每次有人被添加到房间时，都需要将它们添加到队列中。

我需要在程序中创建自己的队列对象，并在对象中编写方法以添加到队列并从队列中获取。

每次将客户添加到房间时，都应该使用队列对象方法，将客户的名称添加到队列中。

当用户选择显示最后3个客户的名称时，代码应逐个从队列中删除它们（先进先出）并在删除时显示它们。

队列应该基于一个数组并保存7个项目。

当队列项到达数组末尾时，应将它们添加到开头或数组中。

如果队列已满，则应显示错误消息，并且最早的队列项应自动删除并显示。

这是主体：

package hotelcoursework2;

import java.util.*;

public class HotelCourseWork2 {

    public static void main(String[] args) {

        Room[] myHotel = new Room[10];
        Queue mq = new Queue();

        int guests = 0;    
        String roomName = null;
        int roomNum = 0;
        String letter = "";

        for (int i = 0; i < myHotel.length; i++) {
            myHotel[i] = new Room();

        }

        do {
            System.out.println("Press E to display empty rooms");
            System.out.println("Press A to add customers to room");
            System.out.println("Press V to view all rooms ");                  
            System.out.println("Press D to delete customers from rooms");
            System.out.println("Or enter 1 to add to queue, 2 to take from queue or 3 display queue");
            System.out.println("Press S to save");
            System.out.println("Press L to load");
            System.out.println("Press X to exit");
            System.out.println("Enter a Letter: ");
            Scanner scan = new Scanner(System.in);
            letter = scan.next();

            if (letter.equals("A")) {
                add(myHotel, roomNum, roomName, guests);

                mq.addqueue();
            }
            if (letter.equals("V")) {
                view(myHotel);
            }      
            if (letter.equals("E")){
                empty(myHotel);
            }

            if(letter.equals("D")){
                delete(myHotel, roomNum);
                mq.takequeue();
           }

            if (letter.equals("S")){

            }    

            if(letter.equals("3")){
                mq.displayqueue();
            }


        } while (letter.charAt(0) != 'X');
        System.out.println("Exit successfull");

    }


   private static void add(Room myHotel[], int roomNum, String roomName, int guests) {
        Scanner input = new Scanner(System.in);
        System.out.println("Enter room number (0-9) or 10 to stop:");
        roomNum = input.nextInt();
        if (roomNum == 10) {
            System.out.println("Exit successful");
            System.exit(0);
        }
        System.out.println("Enter name for room " + roomNum + " :");
        roomName = input.next();
        myHotel[roomNum].setName(roomName);
        System.out.println("Enter how many guests: ");
        guests = input.nextInt();
        myHotel[roomNum].setGuestsInRoom(guests);
        System.out.println("Add customers to queue: ");


        for (int i = 0; i < 10; i++) {
            System.out.println("Customer " + myHotel[i].getName() + " has been allocated to room " + i
             + " with " + myHotel[i].getGuestsInRoom() + " guests. ");

        }
    }

   private static void view(Room myHotel[]) {

        for (int i = 0; i < 10; i++) {
            System.out.println("room " + i + " occupied by " + myHotel[i].getName() );
        }
    }

   private static void empty(Room myHotel[]) {
        for (int i = 0; i < 10; i++) {
            if (myHotel[i].getName().equals("no-one")) {
                System.out.println("room " + i + " is empty");
            }
        }
    }

   private static void delete(Room myHotel[], int roomNum){
        Scanner input = new Scanner(System.in);
        System.out.println("Enter room number you want to delete a customer from: ");
        roomNum = input.nextInt();
        myHotel[roomNum].setName("no-one");

   }



}

这是我为队列创建的类，但现在我被卡住了。队列应该先进先出。

package hotelcoursework2;
import java.util.Scanner;

public class Queue {

    // be careful - this queue can go over the end of the array
    //the array should be used in a circular way
    private static String qitems[] = new String[7];
    private static int front = 0, end = 0;

    static void addqueue() {
        Scanner input = new Scanner(System.in);
        System.out.print("Enter someone to the queue :");
        qitems[end] = input.next();
        end++;

    }

    static void takequeue() {
        if (end > front) {
            System.out.println("Person remove :" + qitems[front]);
            front++;
        } else {
            System.out.println("Empty queue");
        }
    }

    static void displayqueue() {
        System.out.println("Queue display: ");
        for (int look = front; look < end; look++) {
            System.out.print(" " + qitems[look]);
        }
        System.out.println("");
    }

}

Answer 1

所以基本上你想知道如何实现一个简单的队列。

除非必须，否则使用数组会更复杂，因为您必须处理调整数组大小并移动其内容。

最简单的队列结构是一个链表，如下所示：

public class Queue<T>
{
  private Node head;
  private Node tail;

  public void add(T value)
  {
    if (head == null)
    {
      head = new Node(null, value);
      tail = head;  
    }
    else
    {
      tail = new Node(tail, value);
    }
  }

  public T peek()
  {
    return head == null ? null : head.value;
  }

  public T take()
  {
    if (head == null)
    {
      return null;
    }
    else
    {
      T value = head.value;
      head = head.next;
      return value;
    }
  }

  @Override
  public String toString()
  {
    StringBuilder stringBuilder = new StringBuilder();

    stringBuilder.append("[");

    Node current = head;
    while (current != null)
    {
      stringBuilder.append(current.value).append(",");
      current = current.next;
    }

    return stringBuilder.replace(stringBuilder.length() - 1, stringBuilder.length(), "]").toString();
  }

  private class Node
  {
    private Node next;
    private T value;

    public Node(Node previous, T value)
    {
      this.value = value;

      if (previous != null)
      {
        previous.next = this;
      }
    }
  }
}

当添加新值并修改head引用时，此类会引用tail和Node Node调整head链中的引用当取值时。

java - 需要帮助的队列方法

1 个答案: