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POJava TableModel implementation crashes the program
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copied!<p>In my program I wish to show some data in a <code>JTable</code>. I have a class containing the data, so the easiest way to present it in a <code>JTable</code> seems to extend my class so that it implements <code>TableModel</code> interface and use it as a model for <code>JTable</code>. Unfortunately it does not work correctly for me. When the program is about to draw the <code>JTable</code>, a <code>NullPointerException</code> is thrown at <code>javax.swing.JTable.prepareRenderer()</code>. Why?</p> <pre><code>package bridgecalc; import java.util.HashSet; import javax.swing.event.TableModelListener; import javax.swing.table.TableModel; public class MyTableModel extends MyDataClass implements TableModel { private static final long serialVersionUID = 1L; // private Object[][] data; //this is in fact declared in the superclass private static final String[] colNames = {"bla", "blabla", "hola", "hej", "egle", "begle", "eciepecie"}; private HashSet<TableModelListener> listeners; public MyTableModel() { data = new Object[7][7]; listeners = new HashSet<TableModelListener>(); } @Override public int getColumnCount() { return data.length; } @Override public int getRowCount() { return data[0].length; } @Override public Object getValueAt(int arg0, int arg1) { return data[arg0][arg1]; } @Override public void addTableModelListener(TableModelListener l) { listeners.add(l); } @Override public Class<?> getColumnClass(int columnIndex) { return null; } @Override public String getColumnName(int columnIndex) { return colNames[columnIndex]; } @Override public boolean isCellEditable(int rowIndex, int columnIndex) { if (rowIndex == columnIndex) return false; else return true; } @Override public void removeTableModelListener(TableModelListener l) { listeners.remove(l); } @Override public void setValueAt(Object aValue, int rowIndex, int columnIndex) { data[columnIndex][rowIndex] = aValue; } } </code></pre> <p>And somewhere in the program:</p> <pre><code>... JTable table = new JTable(new MyTableModel()); this.setViewportView(table); ... </code></pre> <p>Thanks in advance for any help.</p>

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