Adding 2-d ArrayList to JTable

[Liana Norpunova]

Hi!

I've spent 4 hours trying to read the data from file to ArrayList and then to JTable, but still cannot solve one problem.

I have the following class UserDataRow, where the data about a user is described:

   
public class UserDataRow {
    public String regnumber;
    public String firstname;
    public String lastname;
    public String profession;
    public String sex;
    public String dateofbirth;
    public int size;

    public UserDataRow(String rn, String fn, String ln, String p, String s, String dob) {
        this.regnumber = rn;
        this.firstname = fn;
        this.lastname = ln;
        this.profession = p;
        this.sex = s;
        this.dateofbirth = dob;
        this.size = 6;
    }

    public String getRegNum()
    {
        String regnumber = this.regnumber;
        return regnumber;
    }

    public String getFirstName()
    {
        String firstname = this.firstname;
        return firstname;
    }

    public String getLastName()
    {
        String lastname = this.lastname;
        return lastname;
    }

    public String getProfession()
    {
        String profession = this.profession;
        return profession;
    }

    public String getSex()
    {
        String sex = this.sex;
        return sex;
    }

    public String getDateofBirth()
    {
        String dateofbirth = this.dateofbirth;
        return dateofbirth;
    }
}

I'm using the following code to read the data from file:

    
public void readuserdatafromfile() throws IOException {
        try{
            FileInputStream fstream = new FileInputStream("src/filetree/UserDataFile.txt");
            // Get the object of DataInputStream
            DataInputStream in = new DataInputStream(fstream);
            BufferedReader br = new BufferedReader(new InputStreamReader(in));
            String strLine = "";
            String[] tokens = strLine.split(", ");
            //Read file line by line
            UserDataRow p;
            while ((strLine = br.readLine()) != null)   {
              // Copy the content into the array
              tokens = strLine.split(", ");
              userdatarow.add(new UserDataRow(tokens[1], tokens[2], tokens[3], tokens[4], tokens[5], tokens[6]));
              listofusers.add(userdatarow);
            }
            //Close the input stream
            in.close();
            } catch (Exception e){//Catch exception if any
              System.err.println("Error: " + e.getMessage());
            }
    }

Now I want just to put this 2d array "listofusers" into my JTable, but I cannot... The above code does't work.

  
try {
           DefaultTableModel aModel = (DefaultTableModel)filetree.Form.tableDetails.getModel();
           Object d1[][]=(Object[][]) filetree.Form.listofusers.toArray();
           for (int i=0;i<d1.length;i++) {
               for (int j=0;j<d1[i].length;j++) {
                aModel.addRow(new Object[]{d1[i][j]});
               }
           }
           aModel.setColumnIdentifiers(new String [] {"Reg.Nr", "Name",
                          "Surename",
                          "Profession",
                          "Sex",
                          "Date of Birth"});
        } catch (Exception e){
              System.err.println("Error: " + e.getMessage());
        }

The error message is:

    
Error: 6
Error: [Ljava.lang.Object; cannot be cast to [[Ljava.lang.Object;

So, where could be my error?

[Rob Spoor]

Collection.toArray() returns an Object[]. Even though its elements may be Object[] themselves, the array is still an Object[], not an Object[][]. Try the following:

Object d1[][] = filetree.Form.listofusers.toArray(new Object[0][]);

Note that you no longer need to cast. Check out the Javadoc of Collection.toArray(T[]) for more information.

[Greg Charles]

Yeah, that's a bit hard to read. It's saying you are casting a two-dimensional array to a one-dimensional one. Like Object[][] to Object[]. I didn't read through all your code, but try to look for something like that.

ETA: Oops, beaten by 20 seconds and a better answer!

[Liana Norpunova]

Hi!

I've tried Object d1[][] = filetree.Form.listofusers.toArray(new Object[0][]); Now I get only one error message:

Error: 6

What does it mean?

[Wouter Oet]

Are you aware that this:

String dateofbirth = this.dateofbirth;
return dateofbirth;

Does the same as:

return dateofbirth; // By the way isn't dateOfBirth easier to read

I don't know what is in the file but are you sure you want to do this:

userdatarow.add(new UserDataRow(tokens[1], tokens[2], tokens[3], tokens[4], tokens[5], tokens[6]));

and not this:

userdatarow.add(new UserDataRow(tokens[0], tokens[1], tokens[2], tokens[3], tokens[4], tokens[5]));  

It just looks weird to me.

[Liana Norpunova]

Thanks! Now I use one-dimensional array. There are no errors in the code. But the table is empty. Any advises pliz?

    
public static ArrayList<UserDataRow> listofusers = new ArrayList<UserDataRow>();
...    
public void readuserdatafromfile() throws IOException {
        try{
            BufferedReader br = new BufferedReader(new FileReader("src/filetree/UserDataFile.txt"));
            String strLine = "";
            String[] tokens = strLine.split(", ");
            //Read file line by line
            while ((strLine = br.readLine()) != null)   {
              // Copy the content into the array
              tokens = strLine.split(", ");
              listofusers.add(new UserDataRow(tokens[0], tokens[1], tokens[2], tokens[3], tokens[4], tokens[5]));
            }
            br.close();
            } catch (Exception e){//Catch exception if any
              System.err.println("Error: " + listofusers.size());
            }
    }

    
try {
           DefaultTableModel aModel = new DefaultTableModel();
           filetree.Form.tableDetails.setModel(aModel);
           Object d1[] = filetree.Form.listofusers.toArray();
           for (int i=0;i<d1.length;i++) {
                aModel.addRow(new Object[]{d1[i]});
           }
           aModel.setColumnIdentifiers(new String [] {"Reg.Nr.", "Name",
                          "Surename",
                          "Profession",
                          "Sex",
                         "Date of birth"});
        } catch (Exception e){
              System.err.println("Error: " + e.getMessage());
        }

[pete stein]

While you have a one-dimensional Object[] array present, each item in this array is a UserDataRow object, and you are adding these items as rows to the table model. I don't know how the DefaultTableModel will be able to interpret that since it only knows how to handle Object arrays or Vectors as rows. One solution: create an Object[] array within the for loop to use as a row and add it to the model, or 2: create and use an AbstractTableModel that knows how to handle UserDataRow objects (this way is harder).

To clarify, this:

           for (int i=0;i<d1.length;i++) {
                aModel.addRow(new Object[]{d1[i]});
           }

adds an Object array as a row to the table model, but this Object array has one and only one element, a UserDataRow object. Better would be to do something like so (semi-pseudo-code):

           for (int i=0;i<d1.length;i++) {
                Object[] row = new Object[columnCount]; // columnCount = the number of columns in the JTable
                UserDataRow userDataRow = d1[i];
                row[0] = get item in userDataRow to go in first column of table
                row[1] = get item in userDataRow to go in second column of table
                row[3] = get item in userDataRow to go in third column of table
                ..... etc...
                aModel.addRow(row);
           }

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