trying to debug and keep getting Exception in thread "main" java.lang.NullPointerExce

[toamille]

For this class project, i have to read a listings.txt file and out put to overviewfile.txt. at line 23 i get the message Exception in thread "main" java.lang.NullPointerException
at ket.task2.b.KetTask2B.main

public static void main(String[] args) throws FileNotFoundException, IOException
	    {
	 
	     // calls for the input file names
	 
	        Scanner console = new Scanner(System.in);
	        System.out.print("Type in the name of the file - listings.txt -: ");
	        String inputFile = console.next();
	 
	  
	     // writes to the new file overview.txt
	        File input = new File(inputFile);
	        PrintWriter out = new PrintWriter("overview.txt");
	        
	        BufferedReader in = new BufferedReader(new FileReader(input));
	        int count = 0;
	        double sum = 0;
	        
                // put the sum and count for the properities
           String content = null;
	            count++;
                   
           String [] propertylist = content.split("[\\s}]");
             
                    Double propertyvalue = Double.parseDouble(propertylist [2]);
                     for (int i=0; i < propertylist.length; i++)
                     sum += propertyvalue; 	            
	            System.out.println("Total properties listed:  " + count);
	            System.out.println("Total value of properties listed: " + sum);
	            in.close();
		 
	   try {
	 
	        ArrayList<String> propids = new ArrayList<String>();
	        Scanner idfile = new Scanner((input));
	 
	          //print property ids
	           while (idfile.hasNextLine())
	           {              
	             content = idfile.nextLine();
	             String[] fields = content.split("[\\s}]");
	             String propertyids = (fields [0]);
	                  
	             for (int j = 0; j < fields.length; j++)
	                   {
	                    propids.add(propertyids);
	                    System.out.println(propertyids);
	                    in.close();
	                   }
	                }
                   
	          //close Print Writer
	                out.flush();
	            out.close();
	          }catch(Exception e){
	                System.out.println("There was a problem:" + e);
	                   }
	             
            }
	        
	}

[KevinWorkman]

Look at line 20. Then look at line 23. See the problem? You can't dereference a null value.

[toamille]

here is my fix,

 while ((content = in.readLine())!= null)    
	            {
	            count++;
           String [] propertylist = content.split("[\\s}]");

but now i get Exception in thread "main" java.lang.NumberFormatException: empty String
at sun.misc.FloatingDecimal.readJavaFormatString(Floa tingDecimal.java:1011)
at java.lang.Double.parseDouble(
at ket.task2.b.KetTask2B.main

here is new improved code

 // calls for the input file names
	 
	        Scanner console = new Scanner(System.in);
	        System.out.print("Type in the name of the file - listings.txt -: ");
	        String inputFile = console.next();
	 
	  
	     // writes to the new file overview.txt
	        File input = new File(inputFile);
	        PrintWriter out = new PrintWriter("overview.txt");
	        
	        BufferedReader in = new BufferedReader(new FileReader(input));
	        int count = 0;
	        double sum = 0;
	        
                // put the sum and count for the properities
          while ((content = in.readLine())!= null)    
	            {
	            count++;
           String [] propertylist = content.split("[\\s}]");
             
       Double propertyvalue = Double.parseDouble(propertylist [2]);
                     for (int i=0; i < propertylist.length; i++)
                     
                     sum += propertyvalue; 	
                     }
	            System.out.println("Total properties listed:  " + count);
	            System.out.println("Total value of properties listed: " + sum);
	            in.close();
		 
	   try {
	 
	        ArrayList<String> propids = new ArrayList<String>();
	        Scanner idfile = new Scanner((input));
	 
	          //print property ids
	           while (idfile.hasNextLine())
	           {              
	             content = idfile.nextLine();
	             String[] fields = content.split("[\\s}]");
	             String propertyids = (fields [0]);
	                  
	             for (int j = 0; j < fields.length; j++)
	                   {
	                    propids.add(propertyids);
	                    System.out.println(propertyids);
	                    in.close();
	                   }
	                }
                   
	          //close Print Writer
	                out.flush();
	            out.close();
	          }catch(Exception e){
	                System.out.println("There was a problem:" + e);
	                   }
	             
            }
	        }

[KevinWorkman]

What String are you trying to read in? What are you trying to do with it?

[toamille]

the .txt document has a list of properties and a list of values. I need to be able to count the property and sum the values. this portion of code should add up the total property value and out.println() im trying to split what is counted and whats is a sum. Im not sure if that answers the question or not?

[KevinWorkman]

Not really. Print the line out as soon as you read it in, before you do anything with it. What is that value? What are you trying to do with that value that causes the error?

[toamille]

Example listings.txt file:

110001 commercial 500000.00 101
110223 residential 100000.00 101
110020 commercial 1000000.00 107
110333 land 30000.00 105
110442 farm 200000.00 106
110421 land 40000.00 107
112352 residential 250000.00 110

this is what i want it to look like ##

Total properties listed: 7
Total value of properties listed: 2120000.00

110001
110020
110223
110333
110421
110442
112352

this is the print out.
110001
110001
110001
110001
110001
110020
110020
110020
110020
110020
110223
110223
110223
110333
110421
110421
110421
110442
112352

[KevinWorkman]

What I'm trying to get at is what value is causing the error. The error says you're passing an empty String to the parseDouble() method. Why is that? You can figure that out by running your program with a debugger and stepping through it, or by adding strategic print statements to figure out where that empty String is coming from. Does your program read some of the file, and fail in the middle? Does it not read anything in correctly? Does it only fail at the end? These are the kinds of questions you should be asking yourself.

[toamille]

so i changed some things around, and now i'm stuck back on java.lang.NullPointerException at the split. when i add in a try catch. i just get the list of property ids. (see above) so i know its reading the file. how do i get past the null pointer?

while ((content = in.readLine())!= null)    
                     
           {
	            count++;
	    
	            String [] propertylist = line.split("[\\s}]");
	 
	            	           {
	                sum += Double.parseDouble(propertylist [2]);
	               }
	            }

[KevinWorkman]

You have to use a debugger or some print statements to figure out what's going on. For example, what is content each time? What is line? What is propertylist?

[toamille]

I added System.out.println(content); right before the error. I get as output
Type in the name of the file - listings.txt -: listings.txt
110001 commercial 500000.00 101
Exception in thread "main" java.lang.NullPointerException

So how do i get it to read the whole file? that is just the first line. I believe i want "content" to be the whole file...?

[KevinWorkman]

I added System.out.println(content); right before the error. I get as output
Type in the name of the file - listings.txt -: listings.txt
110001 commercial 500000.00 101
Exception in thread "main" java.lang.NullPointerException

Okay, so that's content. What's propertylist? What's line?

So how do i get it to read the whole file? that is just the first line. I believe i want "content" to be the whole file...?

Your program is reading in a single line, and then encountering an error, which prevents the program from continuing to read the file. Your job is to figure out what's causing that error, and you'll do that by finding out the answers to the questions I've been asking.

[toamille]

working good now!!! Found the mistake myself. But some where i messed up and it will output file "overview.txt," but doesn't write anything to it. looking for a proof read to get the text into the text file....?

{
	 
	     // calls for the input file names
	 
	        Scanner console = new Scanner(System.in);
	        System.out.print("Type in the name of the file - listings.txt -: ");
	        String inputFile = console.next();
	 
	  
	     // writes to the new file overview.txt
	        
                PrintWriter out = new PrintWriter("overview.txt");
	        File input = new File(inputFile);
                
	        BufferedReader in = new BufferedReader(new FileReader(input));
                String content = null;
	        int count = 0;
	        double sum = 0;
	      
         try 
         {
                // put the sum and count for the properities
          while ((content = in.readLine())!= null)              
           {
     	            count++;
         //System.out.println(content);	        
          String [] propertylist = content.split("[\\s}]");
//System.out.println(content)
         {       
	  sum += Double.parseDouble(propertylist [0]);
	               
	            }
           }
          //this is the output lines for count and sum 
	            System.out.println("Total properties listed:  " + count);
	            System.out.println("Total value of properties listed: " + sum);
	            //in.close();                  
         
         }catch(IOException | NumberFormatException e){
	                System.out.println("There was a problem:" + e);
	                   }

	   
	        ArrayList<String> propids = new ArrayList<String>();
	        Scanner idfile = new Scanner((input));
	 
	          //print property ids
	           while (idfile.hasNextLine())
	           {              
	             content = idfile.nextLine();
	             String[] fields = content.split("[\\s}]");
	             String propertyids = (fields [0]);
	                
	                   {
	                    propids.add(propertyids);
	                    System.out.println(propertyids);
	                    //in.close();
	                   }
	                }
                   
	          //close Print Writer
	                out.flush();
	            out.close();
	          }
	             
            }

[KevinWorkman]

Found the mistake myself.

Guess it had nothing to do with me asking questions pointing you directly at the problem. I'll be on my way now.

I've given you a process of asking questions about the error. You need to follow that. All you're doing is asking other people to debug your code for you, when you should be trying to answer questions like the ones I asked you before. Where do you think it should write to the file? Is that executing? Why or why not?

[toamille]

Found it, lessons learned. If you copy paste from the top to the bottom, the mistakes just repeats. Forgot to delete the system. from system.out.println ()

                     out.println(propertyids);
	                    //in.close();
	                   }
	                }
                   System.out.print("The Overview file is ready to read: ");
	          //closes Print Writer