Thread: Passed array value is null

2nd part of a homework project which we have strict instructions. In the first part, I have another class which builds an Array of Country objects, which I use to create a Stack. Then the Stack values are supposed to be inserted into the priority Que and sorted alphebetically. Either my stack is not passing the objects correctly, or for whatever reason the priority Que is not receiving them correctly. When I print the array in pQue1 and pQue 2 it returns

null

thanks for any help!

I am very new to java and programming, but from past experiences I feel like the problem lies somewhere in creating the arrays, or somehow I have programmed the methods to pass the array to a completely different instance of priorityQueue??

import java.util.Arrays;
 
public class Stack {
private int maxSize;        // size of stack array
private Countries[] stackArray;  //  recall:  ‘instance variables’
private int top;            // top of stack
private PriorityQueue pQue1; 
private PriorityQueue pQue2; 
 
public Stack(int s)         
  {                
  maxSize = s;             
  stackArray = new Countries[maxSize];           
  top = -1; 
  pQue1 = new PriorityQueue(maxSize);
  pQue2 = new PriorityQueue(maxSize);
 
  } // end constructor
 
  public void push(Countries j)  
  {
  // put item on top of stack
  stackArray[++top] = j;
  System.out.println(stackArray[top]);     
 
  if (stackArray[top].getRegionNumber() == 1 )
      buildPQue1(stackArray[top]);
      pQue1.insert(stackArray[top]);
 
  if  (stackArray[top].getRegionNumber() == 2 )
      buildPQue2(stackArray[top]);
  } // end push
 
  public void buildPQue1(Countries k)
  {         
      pQue1.insert(k);         
  } // end build PQue1()
 
  public void buildPQue2(Countries i)
  {
     pQue1.insert(i);         
  } // end build P Que 2
  // end push()
 
 
 
 
public class PriorityQueue extends Queue
{    // array in sorted order, from max at 0 to min at nitems-1
private int maxSize;
private Countries[] queArray;
private Countries[] item;
private int nItems;
 
 
  public PriorityQueue(int s)    
  {      // constructor             
  super(s);
  maxSize = s;
  queArray = new Countries[maxSize];
  item = new Countries[maxSize];
  }//end constructor
 
  @Override
  public void insert(Countries item)  {     
  int j;                
  if (nItems==0)                           
  {
      queArray[nItems++] = item; 
     // System.out.println(queArray[nItems]);
  }// end if
  else                                         
  {                     
     for (j=nItems-1; j>=0; j--)    
     {
         if (item.getName().compareTo(queArray[j].getName()) < 0 )                                
           queArray[j+1] = queArray[j];                   
        else                                                      
           break;                                            
     } // end for
     if ( j < maxSize)
     {
     queArray[j+1] = item;                                           
     } // end if
       // System.out.print(queArray[j]);
     nItems++;                                                         
 
}  // end else (nItems > 0)          
}  // end insert()
 
public Countries peekMin()            // peek at minimum item
{ 
return queArray[nItems-1]; 
} // end peek min
 
 
public void displayQue()
{
System.out.println(queArray[nItems]);
} // end display que
 
}  // end class PriorityQ

2nd part of a homework project which we have strict instructions. In the first part, I have another class which builds an Array of Country objects, which I use to create a Stack. Then the Stack values are supposed to be inserted into the priority Que and sorted alphebetically. Either my stack is not passing the objects correctly, or for whatever reason the priority Que is not receiving them correctly. When I print the array in pQue1 and pQue 2 it returns

null

thanks for any help!

I am very new to java and programming, but from past experiences I feel like the problem lies somewhere in creating the arrays, or somehow I have programmed the methods to pass the array to a completely different instance of priorityQueue??

i/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
 
/**
 *
 * @author Jason
 */
    import java.util.Arrays;
 
public class Stack {
   private int maxSize;        // size of stack array
   private Countries[] stackArray;  //  recall:  ‘instance variables’
   private int top;            // top of stack
   private PriorityQueue pQue1; 
   private PriorityQueue pQue2; 
 
   public Stack(int s)         
      {			       
      maxSize = s;             
      stackArray = new Countries[maxSize];           
      top = -1; 
 
 
 
      } // end constructor
 
      public void push(Countries j)  
      {
      // put item on top of stack
      stackArray[++top] = j;
     // System.out.println(stackArray[top]);     
 
      pQue1 = new PriorityQueue(maxSize);
      pQue2 = new PriorityQueue(maxSize);
 
      if (stackArray[top].getRegionNumber() == 1 )
          buildPQue1(stackArray[top]);
 
      if  (stackArray[top].getRegionNumber() == 2 )
          buildPQue2(stackArray[top]);
      } // end push
 
      public void buildPQue1(Countries k)
      {         
          pQue1.insert(k);         
      } // end build PQue1()
 
      public void buildPQue2(Countries i)
      {
         pQue1.insert(i);         
      } // end build P Que 2
      // end push()
 
      public Countries pop() 
      {// take item from top of stack
      return stackArray[top--];  
      }// end pop ()
 
      public Countries peek()  
      {       
      return stackArray[top];				
      }  // end peek()
 
      public boolean isEmpty()  
      {  
      return (top == -1);				
      } // end is Empty()
 
      public boolean isFull()   
      {  // true if stack is full        
      return (top == maxSize-1);		
      }  // end is Full()
 
 
 
}//end class Stack
 
/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
 
/**
 *
 * @author Jason
 */
public class PriorityQueue { // array in sorted order, from max at 0 to min at nitems-1
   private int maxSize;
   private Countries[] queArray;
   private Countries[] item;
   private int nItems;
   private Stack stack;
 
 
   public PriorityQueue(int s)    
   {      // constructor             
      stack = new Stack(s);
      maxSize = s;
      queArray = new Countries[maxSize];
      item = new Countries[maxSize];
   }//end constructor
 
 
   public void insert(Countries item)  {     
      int j;				
      if (nItems==0)                           
      {
          queArray[nItems++] = item; 
         // System.out.println(queArray[nItems]);
      }// end if
      else                                         
      {				        
         for (j=nItems-1; j>=0; j--)    
         {
             if (item.getName().compareTo(queArray[j].getName()) < 0 )                     	          
               queArray[j+1] = queArray[j];        	          
            else                                     		          
               break;                              		         
         } // end for
         if ( j < maxSize)
         {
         queArray[j+1] = item;                                           
         } // end if
           // System.out.print(queArray[j]);
         nItems++;                                                         
 
    }  // end else (nItems > 0)	         
    }  // end insert()
 
public Countries peekMin()            // peek at minimum item
    { 
    return queArray[nItems-1]; 
    } // end peek min
 
 
public void displayQue()
    {
 
  for ( int i = 0; i < nItems; ++i ) {
     System.out.println( queArray[i] );
  }
    } // end display que
 
}  // end class PriorityQ`

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