Removing rows from DefaultTableModel

[Jennifer Sohl]

Hi. I am trying to figure out how to remove a row from a table.
I created a table by passing it a model I created that extends DefaultTableModel.
I also have a button in this app so whenever the button is pushed, it should run the method removeRow(int arg) from the model class I created. However, when I do this, I keep getting an ArrayIndexOutOfBounds error indicating that whatever row number I told it to remove is >= 0.
Not sure what this means? Listed below is my class extending DefaultTableModel if that helps any. I have no idea what I'm doing wrong?
Could someone clue me in?
Thanks in advance!

private class TestModel extends DefaultTableModel {
int columns = 3;
String columnNames[] = {"First","Middle","Last"};
Vector dataRows;
String[] rowData;

Object[][] data = {
{"Mary", "L","Campione"},
{"Alison", "A","Huml"}, 
{"Kathy", "B","Walrath"},
{"Sharon", "K","Zakhour"},
{"Philip", "F","Milne"}, 
};
void setData() {
dataRows = new Vector();
// Loop through rows
for(int i = 0; i < data.length; i++) {

rowData = new String[columns];
for(int j = 0; j < columns; j++) {
switch(j) {
case 0:
rowData[j] = data[i][0].toString();
break;
case 1:
rowData[j] = data[i][1].toString();
break;
case 2:
rowData[j] = data[i][2].toString();
}
}
dataRows.addElement(rowData);
}
fireTableChanged(null);
}
public int getColumnCount() {
return columnNames.length;
}
public int getRowCount() {
if(dataRows == null) {
return 0;
}
else {
return dataRows.size();
}
}
public Object getValueAt(int row, int column) {
return ((String[])(dataRows.elementAt(row)))[column];
}
public String getColumnName(int column) {
return columnNames[column] == null ? "No Name" : columnNames[column];
}
public boolean isCellEditable(int row, int column) {
return false;
}
}  

[Jose Botella]

I think the problem is that the default constructor for your class calls parent DefaultTableModel() constructor. According to the API this one creates a table with zero rows and zero columns.
You can use one of the overloaded DefaultTableModel.setDataVector(...) method at the end of setData; which by the way, it seems to be performing the funtion of a constructor.
Alternatively use a constructor in your class that calls super(dataRows, vectorOfColumns)

[Eddie Vanda]

Jennifer,
Check the documentation for the DefaultTableModel, and you'll find it stores data in a vector called dataVector, similar to your dataRows. Your code would work a lot better if you changed all references to dataRows to dataVector which you inherit from DefaultTableModel. You could delete dataRows from your own class. Hope that makes sense.

[Jennifer Sohl]

Thanks for the help guys. However, in the meantime, I did a little more research and found it is best not to extend DefaultTableModel, but AbstractTableModel. So I found a class someone created on the web that is a JTable which contains the code in it to add and remove rows/columns using AbstractTableModel. So far it works great. In this class, there is some code for adding a TableSorter. I can get it to run, but I can't seem to get it to do anything. Whenever I click on the table headers, nothing happens. Could someone maybe look at this and tell me why?? I just don't get it.
Thanks in advance.!
Here's the class I found on the web:

public class SKTable extends JTable {
  Vector columns;
  Vector rows;   
  
  public SKTable(String c[]) {
super();    
// We create the rows and columns.
rows = new Vector();
columns = new Vector();    
// We add the columns
for (int i = 0; i < c.length; i++)
  columns.addElement(c[i]);
this.setModel(new SKTableModel());

this.getSelectionModel().setSelectionInterval(0, 0);    
// Set table font...
this.setFont(new Font("SansSerif", Font.PLAIN, 12));
// Set column header fonts..
JTableHeader header = this.getTableHeader();
header.setFont(new Font("SansSerif", Font.BOLD, 12));
  }
  
  //TODO How in the heck do I get this damn sorter to work with this table?????
  public void addSorter() {
TableSorter  sorter = new TableSorter(this.getModel());
sorter.addMouseListenerToHeaderInTable(this);     
//TableSorter sorter = new TableSorter(new SKTableModel());
//JTable tableView = new JTable(sorter);
this.setModel(sorter);
this.setModel(sorter.getModel());
  }
  /**
   * Add row to table and repaint to show changes. 
   * @param f
   */
  public void addRow(Object f[]) {
SKTableModel tm = (SKTableModel)this.getModel();
tm.addRow(f);
this.setModel(tm);
this.resizeAndRepaint();
  }
  
  public void addRowAt(Object f[],int pos) {
  SKTableModel tm = (SKTableModel)this.getModel();  
  tm.addRowAt(f,pos);
  this.setModel(tm);
  this.resizeAndRepaint();  
  }
  /**
   * Remove row from table model and repaint to show changes.
   * @param i
   */
  public void delRow(int i) {
SKTableModel tm = (SKTableModel)this.getModel();
tm.delRow(i);
this.setModel(tm);
this.resizeAndRepaint();
  }
  /**
   * Deletes row(s) from vector that user selected, and repaints to reflect changes.
   * @param rows
   */
  public void deleteRows(int[] rows) {
  SKTableModel tm = (SKTableModel)this.getModel();
  tm.deleteRows(rows);  
  this.setModel(tm);
  this.resizeAndRepaint();
  }
  public void setRow(String f[], int i) {
SKTableModel tm = (SKTableModel)this.getModel();
tm.setRow(f, i);
this.setModel(tm);
this.resizeAndRepaint();
  }
  
  public void delColumn(int c) {
SKTableModel tm = (SKTableModel)this.getModel();
TableColumnModel tcm = this.getColumnModel();
TableColumn tc = tcm.getColumn(c);
tm.delColumn(c);
this.setModel(tm);
this.removeColumn(tc);
this.resizeAndRepaint();
  }
  public void addColumn(String s) {
SKTableModel tm = (SKTableModel)this.getModel();
TableColumn tc = new TableColumn();
tm.addColumn(s);
this.setModel(tm);
tc.setHeaderValue(s);
tc.setIdentifier(s);
this.addColumn(tc);
this.resizeAndRepaint();
  }
  public String getColumnName(int c) {
SKTableModel tm = (SKTableModel)this.getModel();
return tm.getColumnName(c);
  }
  public void setValueAt(String s, int f, int c) {
SKTableModel tm = (SKTableModel)this.getModel();
tm.setValueAt(s, f, c);
this.resizeAndRepaint();
  } 

  public Object getValueAt(int f, int c) {
SKTableModel tm = (SKTableModel)this.getModel();
return tm.getValueAt(f, c);
  }  
  /**
   * Clear all rows from table.
   *
   */
  public void clear() {
SKTableModel tm = (SKTableModel)this.getModel();
int total = tm.getRowCount();
for (int i = 0; i < total; i++)
  tm.delRow(0);   
this.setModel(tm);
this.resizeAndRepaint();
  }
  
  class SKTableModel extends AbstractTableModel {
    
public void addRow(Object f[]) {
  rows.addElement(f);
}
public void addRowAt(Object f[],int pos) {
rows.add(pos,f);
}
public void delRow(int i) {
  rows.removeElementAt(i);
}

public void deleteRows(int[] no) {
// Delete from the last index up to the first so that the delete
// does not cause the as-yet-undeleted indexes to change:
for(int i = no.length-1; i >=0; i--) {
rows.removeElementAt(no[i]);
}
}
public void setRow(String f[], int i) {
  rows.setElementAt(f, i);
}
public void delColumn(int c) {
  columns.removeElementAt(c);
}
public void addColumn(String s) {
  columns.addElement(s);
}
// Return number of rows
public int getRowCount() {
  return rows.size();
}
// Return number of columns
public int getColumnCount() {
  return columns.size();
}
// Returns column name
public String getColumnName(int i) {
  return (String)columns.elementAt(i);
}
// Indicates if a cell is editable.
public boolean isCellEditable(int f, int c) {
  return false;
}
// Returns value of cell at this point.
public Object getValueAt(int f, int c) {
  Object temp[] = (String[])rows.elementAt(f);
      
  return temp[c];
}
// Sets value of the cell
public void setValueAt(Object x, int f, int c) {
  Object temp[] = (String[])rows.elementAt(f);
  temp[c] = x;
  rows.setElementAt(temp, f);
}
  }  

[Jose Botella]

What dou you expected to happen when clicking the table header?
Notice that in the example it is not necessary to call this.setModel(tm); because tm still continues being the model for the table.
By the way, have you taken a look at How to use Tables in the Java Tutorial?
[ February 20, 2004: Message edited by: Jose Botella ]

[Jennifer Sohl]

When I click on the table header, I expect the data in the table to sort depending on which column header I press. This should happen since I have added a mouse listener to the table header.
Since you brought it up, I see your point where tm continues being the table model, I overlooked that. I will remove it.
(Keep in mind, I found this code on the internet )
In regards to your question, have I looked at How to Use Tables, yes I have.
And I thought I understood them, more or less, however I keep running into little problems like the one above, as well as other little nagging questions I have about them.
By the way, can you tell me, or send me somewhere that will tell me WHY AbstractTableModel is better to extend than DefaultTableModel?
Thanks again for all of your help. I really appreciate it.

[Eddie Vanda]

Hi Jennifer,
DefaultTableModel extends AbstractTableModel so either way AbstractTableModel is in your inheritance chain.
AbstractTableModel does not store any data. This is good for you because you're storing the data in your own class. DefaultTableModel has internal data storage implemented similarly to your way of using vectors, so there was a general conflict, in particular because you used a different name for your vector to DefaultTableModel's vector, so it was not overriding it.
I can't find any reference anywhere to the SortedTable reference so I can't really help you with that.
Can anyone help me with copying code from these pages? When I copy and paste into Textpad I find it all in one line and I have to manually put in all the line feeds. I must be doing it wrong - maybe ask this in the beginner's thread.

[Jose Botella]

The problem with DefaultTableModel is that it uses a Vector to store the data which is not considered to be very efficient. But in the case you do not have a lot of data it is easier to use instead of extending AbstractTableModel.
Because you did not post the code for TableSorter I cannot tell what it is wrong wit it. Assuming such class changes the model of the table a TableModelEvent should be fired (i.e. AbstractTable.fireTableChanged(TableModelEvent e) ) for the table to show the changes.
You can take a look at the example
Sorting Columns in the magnificient book Swing 2nd ed. by Pavel and Robinson.
-----------------------------------------------------------------------
Eddie I haven't used Textpad (JEdit is my favourite for quick examples) Have you configure it to java source code?
[ February 22, 2004: Message edited by: Jose Botella ]

[Eddie Vanda]

Jose, yes and thanks. Rather than hijack this page I'll pose the question in the beginner's page.

[Jennifer Sohl]

Thanks for the clarification on Abstract and Default table models! However, I still have the issue with the table sorting... Sorry I didn't post the code earlier. Here it is. Let me know if you need anything else!
Thanks again for helping!

public class TableSorter extends TableMap {
    int             indexes[];
    Vector          sortingColumns = new Vector();
    boolean         ascending = true;
    int compares;
    public TableSorter() {
        indexes = new int[0]; // for consistency
    }
    public TableSorter(TableModel model) {
        setModel(model);
    }
    public void setModel(TableModel model) {
        super.setModel(model);
        reallocateIndexes();
    }
    public int compareRowsByColumn(int row1, int row2, int column) {
        Class type = model.getColumnClass(column);
        TableModel data = model;
        // Check for nulls.
        Object o1 = data.getValueAt(row1, column);
        Object o2 = data.getValueAt(row2, column);
        // If both values are null, return 0.
        if (o1 == null && o2 == null) {
            return 0;
        } else if (o1 == null) { // Define null less than everything.
            return -1;
        } else if (o2 == null) {
            return 1;
        }
        /*
         * We copy all returned values from the getValue call in case
         * an optimised model is reusing one object to return many
         * values.  The Number subclasses in the JDK are immutable and
         * so will not be used in this way but other subclasses of
         * Number might want to do this to save space and avoid
         * unnecessary heap allocation.
         */
        if (type.getSuperclass() == java.lang.Number.class) {
            Number n1 = (Number)data.getValueAt(row1, column);
            double d1 = n1.doubleValue();
            Number n2 = (Number)data.getValueAt(row2, column);
            double d2 = n2.doubleValue();
            if (d1 < d2) {
                return -1;
            } else if (d1 > d2) {
                return 1;
            } else {
                return 0;
            }
        } else if (type == java.util.Date.class) {
            Date d1 = (Date)data.getValueAt(row1, column);
            long n1 = d1.getTime();
            Date d2 = (Date)data.getValueAt(row2, column);
            long n2 = d2.getTime();
            if (n1 < n2) {
                return -1;
            } else if (n1 > n2) {
                return 1;
            } else {
                return 0;
            }
        } else if (type == String.class) {
            String s1 = (String)data.getValueAt(row1, column);
            String s2    = (String)data.getValueAt(row2, column);
            int result = s1.compareTo(s2);
            if (result < 0) {
                return -1;
            } else if (result > 0) {
                return 1;
            } else {
                return 0;
            }
        } else if (type == Boolean.class) {
            Boolean bool1 = (Boolean)data.getValueAt(row1, column);
            boolean b1 = bool1.booleanValue();
            Boolean bool2 = (Boolean)data.getValueAt(row2, column);
            boolean b2 = bool2.booleanValue();
            if (b1 == b2) {
                return 0;
            } else if (b1) { // Define false < true
                return 1;
            } else {
                return -1;
            }
        } else {
            Object v1 = data.getValueAt(row1, column);
            String s1 = v1.toString();
            Object v2 = data.getValueAt(row2, column);
            String s2 = v2.toString();
            int result = s1.compareTo(s2);
            if (result < 0) {
                return -1;
            } else if (result > 0) {
                return 1;
            } else {
        return 0;
            }
        }
    }
    public int compare(int row1, int row2) {
        compares++;
        for (int level = 0; level < sortingColumns.size(); level++) {
            Integer column = (Integer)sortingColumns.elementAt(level);
            int result = compareRowsByColumn(row1, row2, column.intValue());
            if (result != 0) {
                return ascending ? result : -result;
            }
        }
        return 0;
    }
    public void reallocateIndexes() {
        int rowCount = model.getRowCount();
        // Set up a new array of indexes with the right number of elements
        // for the new data model.
        indexes = new int[rowCount];
        // Initialise with the identity mapping.
        for (int row = 0; row < rowCount; row++) {
            indexes[row] = row;
        }
    }
    public void tableChanged(TableModelEvent e) {
        //System.out.println("Sorter: tableChanged");
        reallocateIndexes();
        super.tableChanged(e);
    }
    public void checkModel() {
        if (indexes.length != model.getRowCount()) {
            System.err.println("Sorter not informed of a change in model.");
        }
    }
    public void sort(Object sender) {
        checkModel();
        compares = 0;
        // n2sort();
        // qsort(0, indexes.length-1);
        shuttlesort((int[])indexes.clone(), indexes, 0, indexes.length);
        //System.out.println("Compares: "+compares);
    }
    public void n2sort() {
        for (int i = 0; i < getRowCount(); i++) {
            for (int j = i+1; j < getRowCount(); j++) {
                if (compare(indexes[i], indexes[j]) == -1) {
                    swap(i, j);
                }
            }
        }
    }
    // This is a home-grown implementation which we have not had time
    // to research - it may perform poorly in some circumstances. It
    // requires twice the space of an in-place algorithm and makes
    // NlogN assigments shuttling the values between the two
    // arrays. The number of compares appears to vary between N-1 and
    // NlogN depending on the initial order but the main reason for
    // using it here is that, unlike qsort, it is stable.
    public void shuttlesort(int from[], int to[], int low, int high) {
        if (high - low < 2) {
            return;
        }
        int middle = (low + high)/2;
        shuttlesort(to, from, low, middle);
        shuttlesort(to, from, middle, high);
        int p = low;
        int q = middle;
        /* This is an optional short-cut; at each recursive call,
        check to see if the elements in this subset are already
        ordered.  If so, no further comparisons are needed; the
        sub-array can just be copied.  The array must be copied rather
        than assigned otherwise sister calls in the recursion might
        get out of sinc.  When the number of elements is three they
        are partitioned so that the first set, [low, mid), has one
        element and and the second, [mid, high), has two. We skip the
        optimisation when the number of elements is three or less as
        the first compare in the normal merge will produce the same
        sequence of steps. This optimisation seems to be worthwhile
        for partially ordered lists but some analysis is needed to
        find out how the performance drops to Nlog(N) as the initial
        order diminishes - it may drop very quickly.  */
        if (high - low >= 4 && compare(from[middle-1], from[middle]) <= 0) {
            for (int i = low; i < high; i++) {
                to[i] = from[i];
            }
            return;
        }
        // A normal merge.
        for (int i = low; i < high; i++) {
            if (q >= high || (p < middle && compare(from[p], from[q]) <= 0)) {
                to[i] = from[p++];
            }
            else {
                to[i] = from[q++];
            }
        }
    }
    public void swap(int i, int j) {
        int tmp = indexes[i];
        indexes[i] = indexes[j];
        indexes[j] = tmp;
    }
    // The mapping only affects the contents of the data rows.
    // Pass all requests to these rows through the mapping array: "indexes".
    public Object getValueAt(int aRow, int aColumn) {
        checkModel();
        return model.getValueAt(indexes[aRow], aColumn);
    }
    public void setValueAt(Object aValue, int aRow, int aColumn) {
        checkModel();
        model.setValueAt(aValue, indexes[aRow], aColumn);
    }
    public void sortByColumn(int column) {
        sortByColumn(column, true);
    }
    public void sortByColumn(int column, boolean ascending) {
        this.ascending = ascending;
        sortingColumns.removeAllElements();
        sortingColumns.addElement(new Integer(column));
        sort(this);
        super.tableChanged(new TableModelEvent(this));
    }
    // There is no-where else to put this.
    // Add a mouse listener to the Table to trigger a table sort
    // when a column heading is clicked in the JTable.
    public void addMouseListenerToHeaderInTable(JTable table) {
        final TableSorter sorter = this;
        final JTable tableView = table;
        tableView.setColumnSelectionAllowed(false);
        MouseAdapter listMouseListener = new MouseAdapter() {
            public void mouseClicked(MouseEvent e) {
                TableColumnModel columnModel = tableView.getColumnModel();
                int viewColumn = columnModel.getColumnIndexAtX(e.getX());
                int column = tableView.convertColumnIndexToModel(viewColumn);
                if (e.getClickCount() == 1 && column != -1) {
                    //System.out.println("Sorting ...");
                    //int shiftPressed = e.getModifiers()&InputEvent.SHIFT_MASK;
                    //boolean ascending = (shiftPressed == 0);
                    ascending = !ascending;
                    sorter.sortByColumn(column, ascending);
                }
            }
        };
        JTableHeader th = tableView.getTableHeader();
        th.addMouseListener(listMouseListener);
    }
}  

[Eddie Vanda]

Hi Jennifer,
I've tried to compile your two classes, SKTable & TableSorter, but I seem to be missing TableMap. Do you have a listing for TableMap?
Ed

[Dana Hanna]

Yuck - that code looks like a C programmer...
Most of the classes that special logic is coded for implement "Comparable", and can be sorted automatically utilizing the java.util package...

[Jose Botella]

I knew I had seen this code somewhere else. Sorting and Otherwise Manupulating data in the Java Tutorial explains clearly how to use TableSorter.
I haven't compiled it because I trust the Tutorial.

[Jennifer Sohl]

Okay. I've looked at the tutorial, and the 3 lines of code that it says is required to implement TableSorter. I have successfully done this before in a different application. The only difference with this one, is I am not passing the table constructor the sorter as the model. Instead, the model is being set in the SKTable constructor rather than passed. So everytime I try to click on the header, I am finding the output to the console is "Sorter not informed of change in model", And I don't know why! If I've set the table model to use the sorter, shouldn't it work? I just don't understand what I'm doing wrong.
Thanks again for the help

[Jose Botella]

The idea is that TableSorter should be the model for the table. And the original table's model should be the TableSorter's model.
If you are calling addSorter method, the last sentence:
this.setModel(sorter.getModel()); should be left out because it resets the previous model for the table that was correctly set with: this.setModel(sorter);

[Mathews P Srampikal]

Have a look into this Thread
<a>https://coderanch.com/t/337429/GUI/java/Color-JTable</a>;

[Jennifer Sohl]

I tried removing this.setModel(sorter.getModel), and I'm still getting the same results: "Sorter not informed of change in Model". Right now what I have is in the constructor of SKTable I am calling the following method:

public void setModel(boolean sortable) {
  if(sortable) {
  sorter = new TableSorter(new SKTableModel());
  sorter.addMouseListenerToHeaderInTable(this);
  this.setModel(sorter);  
  }
  else {
  this.setModel(new SKTableModel());
  }
  }  

It seems to me it should be setting the model correctly??
So, any ideas why the sorter is still not getting informed of the changes in the model?
Thanks again for all of your help.

[Jose Botella]

Another point is: the original table's model should notify sorter of changes in the model, and sorter should notify the table.
Extending from DefaultTableModel gives you these notifications for free. Extending from AbstractTableModel don't. But it is easy to write them:

 class SKTableModel extends AbstractTableModel {
public void addRow(Object f[]) {
rows.addElement(f);
fireTableRowsInserted(rows.size()-1, rows.size()-1)
}
.
.
.

Similarly with each of the methods that modify the content of the model. Consult the API for AbstractTableModel.fireXXX methods.
Now, fireXXX methods will notify those listeners registered with AbstractTableModel.addTableModelListener . Notice the registration is done when you call sorter = new TableSorter(new SKTableModel()); by this code in TableMap class:

 public void setModel(TableModel model) {
        this.model = model;
        model.addTableModelListener(this);
    }

In TableMap there is also this piece of code:

Implementation of the TableModelListener interface,
//
    // By default forward all events to all the listeners.
    public void tableChanged(TableModelEvent e) {
        fireTableChanged(e);
    }

That is, our TableSorter listens for changes in SKTableModel,and then passes these events to the TableModelListeners registered with it. The registration of SkTable with TableSorter takes place (according to API for JTable.setModel) when calling this.setModel(sorter); in SKTable.setModel
Hope now it works.