java - 显示和插入方法错误(双端队列)

Question

1)我的问题

当我从右侧或左侧删除时，程序将被删除 true但是当我调用diplay方法时内容错误

像这样我插入 12 43 65 23当从左侧删除程序时，将删除 12但是当调用显示方法时显示如下 12 43 65

当从正确的程序中删除时将删除 23但是当调用显示方法时显示如下 12 43

为什么？？？？ )；

当我尝试在删除后插入时写这个

由于队列已满，无法正确插入。先删除右边，然后你可以插入右边

问题出在哪里？

请帮助我

请

2)我的代码

头等舱

class dqueue
{
    private int fullsize;                    //number of all cells
    private int item_num;                    // number of busy cells only
    private int front,rear;
    public int j;
    private double [] dqarr;
//==========================================
    public dqueue(int s)                      //constructor
    {
        fullsize = s;
        front = 0;
        rear = -1;
        item_num = 0;
        dqarr = new double[fullsize];
    }
//==========================================
    public void insert(double data)
    {
        if (rear == fullsize-1)
            rear = -1;
        rear++;
        dqarr[rear] = data;
        item_num++;

    }
   public double removeLeft() // take item from front of queue
     {
   double temp = dqarr[front++]; // get value and incr front
   if(front == fullsize) 
   front = 0;
   item_num --; // one less item
   return temp;
    }
    public double removeRight() // take item from rear of queue
     {
   double temp = dqarr[rear--]; // get value and decr rear
   if(rear == -1) // 
   rear = item_num -1;
   item_num --; // one less item
   return temp;
    }
//=========================================

     public void display ()                //display items
{
for (int j=0;j<item_num;j++)               // for every element 
System.out.print(dqarr[j] +"  " );          // display it 
System.out.println("");
}

//=========================================
public int size()              //number of items in queue
{
return item_num;
}
//==========================================
public boolean isEmpty()       // true if queue is empty
{
return (item_num ==0);
}


} 

第二类

import java.util.Scanner;
class dqueuetest
{
    public static void main(String[] args)
    {
        Scanner input = new Scanner(System.in);
        System.out.println("              ***** Welcome here***** ");
        System.out.println("              *****  Mind Of Programming Group***** ");
       System.out.println("               _____________________________________________ ");
        System.out.println("enter size of your dqueue");
        int size = input.nextInt();
        dqueue mydq = new dqueue(size);
        System.out.println("");
        System.out.println("enter your itemes");
//=====================================
        for(int i = 0;i<=size-1;i++)
        {
           System.out.printf("item %d:",i+1);
           double item = input.nextDouble();
           mydq.insert(item);
           System.out.println("");
        }    

//=====================================  
int queue =size ;         
int c = 0 ;
while (c != 6)
{
    System.out.println("");
    System.out.println("************************************************");
    System.out.println("               MAIN MENUE");
    System.out.println("1- INSERT RIGHT  ");
    System.out.println("2- REMOVE LEFT");
    System.out.println("3- REMOVE RIGHT");
    System.out.println("4- DISPLAY");
    System.out.println("5- SIZE");
    System.out.println("6- EXIT");  
    System.out.println("************************************************");
    System.out.println("choose your operation by number(1-6)");  
    c = input.nextInt();
    switch  (c)
    {
    case 1:
   if (queue == size)
    System.out.print("Can not insert right because the queue is full . first remove right and then u can insert right   ");
          else { System.out.print("enter your item: ");
           double item = input.nextDouble();
           mydq.insert(item);}
          break;

   case 2:
       System.out.println("REMOVE FROM REAR :");
              if( !mydq.isEmpty() )
    {
  double item = mydq.removeLeft();

  System.out.print(item + "\t");
    } // end while
  System.out.println("");
  mydq.display();

    break;

   case 3:
    System.out.println("REMOVE FROM FRONT :");
            if( !mydq.isEmpty() )
    {
  double item = mydq.removeRight();

  System.out.print(item + "\t");
    } // end while
  System.out.println("");
  mydq.display();
     break;

    case 4:
    System.out.println("The items in Queue are :");  
        mydq.display();
    break;

    case 5:
     System.out.println("The  Size of the Queue is :"+mydq.size());
    break;

    case 6:
    System.out.println("Good Bye");

    break;

    default:
    System.out.println("wrong chiose enter again");
  }       //end switch
 }       //end while
}        // end main     

}//end class

Answer 1

我怀疑最让您困惑的是您的 display 方法...:

public void display ()                //display items
{
    for (int j=0;j<item_num;j++)               // for every element 
        System.out.print(dqarr[j] +"  " );          // display it 
    System.out.println("");
}

在这种方法中，您完全忽略了您编码的队列的“内部逻辑结构”，这主要取决于 front 和 rear 索引:确实，请注意，您在这里甚至没有提及任何一个索引 - 您只是打印“物理上第一个”item_num 元素，这些元素与“逻辑上存在”没有任何关系的。

您需要从第 front 个元素(不是第 0 个元素!)开始并显示 item_num 元素从那里开始(当然，如果您遇到它，则在末尾有环绕)。这将显示队列的逻辑内容，而不是实现它的数组的“随机”切片!-)