DefaultTableModel Overview

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Leahy, Paul. "DefaultTableModel Overview." ThoughtCo, May. 9, 2017, thoughtco.com/defaulttablemodel-overview-2033890. Leahy, Paul. (2017, May 9). DefaultTableModel Overview. Retrieved from https://www.thoughtco.com/defaulttablemodel-overview-2033890 Leahy, Paul. "DefaultTableModel Overview." ThoughtCo. https://www.thoughtco.com/defaulttablemodel-overview-2033890 (accessed September 23, 2017).

The DefaultTableModel class is a subclass of the AbstractTableModel. As the name suggests it is the table model that is used by a JTable when no table model is specifically defined by the programmer. The DefaultTableModel stores the data for the JTable in a Vector of Vectors.

Although the Vector is a legacy Java collection it is still supported and there is no issue with using it unless the additional overhead caused by using a synchronized collection is a problem for your Java application.

The advantage of using the DefaultTableModel over a custom AbstractTableModel is you don't have to code the methods like add, insert or delete rows and columns. They already exist to change the data held in the Vector of Vectors. This makes it a quick and easy table model to implement.

Import Statement

import javax.swing.table.DefaultTableModel;

Constructors

The DefaultTableModel class has six constructors. Each can be used to populate of the DefaultTableModel in different ways.

The first constructor takes no arguments and creates a DefaultTableModel which has no data, zero columns and zero rows:

DefaultTableModel defTableModel = DefaultTableModel();

The next constructor can be used to specify the number of rows and columns of a DefaultTableModel with no data:

DefaultTableModel defTableModel = DefaultTableModel(10, 10);

There are two constructors that can be used to create a DefaultTableModel with column names and a specified number of rows (all containing null values).

One uses an ​Object array to hold the column names, the other ​a Vector:

String[] columnNames = {"Column 1","Column 2","Column 3"};
DefaultTableModel defTableModel = DefaultTableModel(columnNames, 10);

or

DefaultTableModel defTableModel = DefaultTableModel(columnNames, 10);

Finally there are two constructors used to populate the DefaultTableModel with row data along with column names.

One used Object arrays, the other Vectors:

Object[][] data = {{1,1,1},{2,2,2},{3,3,3},{4,4,4}};
String[] columnNames = {"Column 1","Column 2","Column 3"};
DefaultTableModel defTableModel = DefaultTableModel(data, columnNames);

or

Vector rowData = new Vector();
rowData.add(1);
Vector> data = new Vector>();
data.add(0, rowData);
Vector columnNames = new Vector();
columnNames.add("Column 1");
DefaultTableModel defTableModel = DefaultTableModel(data, columnNames);

Useful Methods

To add a row to the DefaultTableModel use the addRow method along with the row data to add:

Object[] newRowData = {5,5,5,5};
defTableModel.addRow(newRowData);

To insert a row use the insertRow method, specifying the row index to insert and the row data:

Object[] insertRowData = {2.5,2.5,2.5,2.5};
defTableModel.insertRow(2,insertRowData);

To delete a row use the removeRow method, specifying the row index to delete:

defTableModel.removeRow(0);

To get a value in a table cell use the getValueAt method. For example, if the data at row 2, column 2 contains an int:

int value = tabModel.getValueAt(2, 2);

To set a value in a table cell setValueAt method with the value to set along with the row and column index:

defTableModel.setValueAt(8888, 3, 2);

Usage Tips

If a JTable is created using the constructor that is passed a two-dimensional array containing the row data and an array containing the column names:

Object[][] data = {{1,1,1},{2,2,2},{3,3,3},{4,4,4}};
String[] columnNames = {"Column 1","Column 2","Column 3"};
JTable exampleJTable = new JTable(data, columnNames);

then the following cast will not work:

DefaultTableModel dft = (DefaultTableModel)exampleJTable.getModel();

A runtime ClassCastException will be thrown because in this instance the DefaultTableModel is declared as an anonymous inner class in the JTable object and cannot be cast. It can only be cast to the TableModel interface. A way around this is to create your own DefaultTableModel and set it to be the model of the JTable:

JTable exampleJTable = new JTable();
DefaultTableModel defTableModel = new DefaultTableModel(data, columnNames);
exampleJTable.setModel(defTableModel);

Then the DefaultTableModel defTableModel can be used to manipulate the data in the JTable.

To see the DefaultTableModel in action have a look at the DefaultTableModel Example Program.