Removing node from private parameter

Question

hey wondering if anyone can help me with some coursework im doing
im trying to remove a record from a queue by using a parameter from a class.
class QueueNode
     private      String      document ;      
     private      String      owner ;      
     private      int           size ;           
     private     QueueNode     next ;
     private     QueueNode     previous ;
     public QueueNode (String document , String owner , int size)
          this.document = document ;
          this.owner = owner ;
          this.size = size ;
          next = null ;
          previous = null ;
     public String getDocument()
          return document ;
     public String getOwner()
          return owner ;
     public int getSize()
          return size ;
     public QueueNode getNext()
          return next ;
     public QueueNode getPrevious()
          return previous ;
     public void setDocument(String document)
          this.document = document ;
     public void setOwner(String owner)
          this.owner = owner ;
     public void setSize(int size)
          this.size = size;
     public void setNext(QueueNode next)
          this.next = next ;
     public void setPrevious(QueueNode previous) //this is the part im having trouble with
          this.previous = previous ;
class Queue           
     private     QueueNode start ;
     private     QueueNode end ;
     public Queue ()     
          start = new QueueNode("","",0) ;
          start = null ;
          end = new QueueNode("","",0) ;
          end = null ;
     public void add ( String document, String owner, int size )
          if ( start == null )
               start = new QueueNode(document,owner,size) ;
               end = start ;          
     else                              
               QueueNode temp = new QueueNode(document,owner,size) ;
               temp.setNext (end) ;                              
               end.setPrevious (temp) ;     
               end = temp ;               
     public boolean isEmpty ()          
          return ( start == null) ;
     public QueueNode remove ()     
          QueueNode temp = new QueueNode("","",0) ;
          if ( start == null )
               return null ;      
          else if ( start.setPrevious == null)
                    temp = start ;
                    start = null ;          
                    return temp ;     
               else
                    temp = start ;     
                    start = start.setPrevious ;     
                    return temp ;                                        
     public void displayAll ()     
          QueueNode temp = new QueueNode ("","",0) ;     
          temp = start ;               
          while ( temp ! = null )     
               System.out.println ( "Document: " + temp.getDocument() ) ;
               System.out.println ( "Owner: " + temp.getOwner() ) ;
               System.out.println ( "Size: " + temp.getSize() ) ;
               temp = temp.setPrevious ;     
and these are the errors im getting
Queue.java:47: cannot resolve symbol
symbol : variable setPrevious
location: class QueueNode
          else if ( start.setPrevious == null)
^
Queue.java:56: cannot resolve symbol
symbol : variable setPrevious
location: class QueueNode
                    start = start.setPrevious ;     
^
Queue.java:74: cannot resolve symbol
symbol : variable setPrevious
location: class QueueNode
               temp = temp.setPrevious ;     
^
3 errors
any help appreciated
thanks

Answer 1

Let's look at the first error:
Queue.java:47: cannot resolve symbol
symbol : variable setPrevious
location: class QueueNode
else if ( start.setPrevious == null) You are confusing the field previous:
private QueueNode previous ;with the method setPrevious:
public void setPrevious(QueueNode previous)
    this.previous = previous ;
}That would be like confusing your weight with trying to lose weight.
Here is how a field might be used:
temp.previous = null;
other = temp.previous;
if (another == temp.previous)Here is how setPrevious is used.
temp.setPrevious(null);Does this make any sense?