Question

我有java代码，并且能够提供一个toString，如下面的代码所示：

       public class CircularArrayQueue<T> implements QueueADT<T>
{
   private final int DEFAULT_CAPACITY = 100;
   private int front, rear, count;
   private T[] queue; 

   //-----------------------------------------------------------------
   //  Creates an empty queue using the default capacity.
   //-----------------------------------------------------------------
   public CircularArrayQueue()
   {
      front = rear = count = 0;
      queue = (T[]) (new Object[DEFAULT_CAPACITY]);
   }

   //-----------------------------------------------------------------
   //  Creates an empty queue using the specified capacity.
   //-----------------------------------------------------------------
   public CircularArrayQueue (int initialCapacity)
   {
      front = rear = count = 0;
      queue = ( (T[])(new Object[initialCapacity]) );
   }

   //-----------------------------------------------------------------
   //  Adds the specified element to the rear of the queue, expanding
   //  the capacity of the queue array if necessary.
   //-----------------------------------------------------------------
   public void enqueue (T element)
   {
      if (size() == queue.length) 
         expandCapacity();

      queue[rear] = element;

      rear = (rear+1) % queue.length;

      count++;
   }

   //-----------------------------------------------------------------
   //  Removes the element at the front of the queue and returns a
   //  reference to it. Throws an EmptyCollectionException if the
   //  queue is empty.
   //-----------------------------------------------------------------
   public T dequeue() throws EmptyCollectionException
   {
      if (isEmpty())
         throw new EmptyCollectionException ("queue");

      T result = queue[front];
      queue[front] = null;

      front = (front+1) % queue.length;

      count--;

      return result;
   }

   //-----------------------------------------------------------------
   //  Returns a reference to the element at the front of the queue.
   //  The element is not removed from the queue.  Throws an
   //  EmptyCollectionException if the queue is empty.  
   //-----------------------------------------------------------------
   public T first() throws EmptyCollectionException
   {
      if (isEmpty())
         throw new EmptyCollectionException ("queue"); 

      return queue[front];
   }

   //-----------------------------------------------------------------
   //  Returns true if this queue is empty and false otherwise. 
   //-----------------------------------------------------------------
   public boolean isEmpty()
   {
      return (count == 0);
   }

   //-----------------------------------------------------------------
   //  Returns the number of elements currently in this queue.
   //-----------------------------------------------------------------
   public int size()
   {
      return count;
   }


   //-----------------------------------------------------------------
   //  Returns a string representation of this queue. 
   //-----------------------------------------------------------------
  public String toString()
  {
    String result = "";
    int scan = 0;

    while(scan < count)
    {
     if(queue[scan]!=null)
     {
       result += queue[scan].toString()+"\n";
     }
    scan++;
    }

    return result;

  }

   //-----------------------------------------------------------------
   //  Creates a new array to store the contents of the queue with
   //  twice the capacity of the old one.
   //-----------------------------------------------------------------
  public void expandCapacity()
  {
    T[] larger = (T[])(new Object[queue.length *2]);   

    for(int scan=0; scan < count; scan++)
    {
      larger[scan] = queue[front];
      front=(front+1) % queue.length;
    }

    front = 0;
    rear = count;
    queue = larger;
  }
}

如何根据队列的这些输出修改我的toString：

我想从一个显示汽车数量的初始字符串开始如果队列为空，那么我将返回初始String。如果前方位于后方或之前我想从前到后为每辆车添加一条线然后为从数组开头到后面1的那些添加行否则我想在前后1之间为每辆车添加一条线。

这是我当前的toString（）：

public String toString()
   {
      String result = "";

      for (int scan=0; scan < rear; scan++) 
         result = result + queue[scan].toString() + "\n";

      return result;
   }

Answer 1

您编写了伪代码，其余几个if / else-if块。

  public String toString()
  {
    String result = String.format("There are %d items in the queue.", count);
    if (count == 0)
    {
      return result;
    }
    else if (front >= back)
    {
      for (int i = front; i < count; i++)
      {
        result += queue[i].toString() + "\n";
      }
      for (int i = 0; i < back; i++)
      {
        result += queue[i].toString() + "\n";
      }
    }
    else
    {
      for (int i = front; i < back; i++)
      {
        result += queue[i].toString() + "\n";
      }
    }
    return result;
  }

修改toString循环数组缓冲区

1 个答案: