JTable duplicate values ​​in string

Question

I have a JTable populated with a custom DataModel (inserted below), and when I call the populate() method, it populates the table with duplicate data - each row is filled with the same value and again. However, upon closer inspection (just using println () in the data field), the data model is not to blame - it contains the correct data in the expected format. What gives?

 import java.util.ArrayList; import javax.swing.table.AbstractTableModel; @SuppressWarnings("serial") // we don't expect this app to ever use serialized classes. EVER. public class CollectionDataModel extends AbstractTableModel { private ArrayList<ArrayList<String>> data; public CollectionDataModel() { data = new ArrayList<ArrayList<String>>(); } @Override public int getColumnCount() { if(data.isEmpty()) return 0; return data.get(0).size(); } @Override public int getRowCount() { return data.size(); } @Override public Object getValueAt(int rowIndex, int columnIndex) { if(rowIndex > getRowCount()) return null; if(columnIndex > getColumnCount()) return null; return data.get(rowIndex).get(columnIndex); } public void populate(Collection c) { data.clear(); for(Item i : c.getItems()) { ArrayList<String> row = new ArrayList<String>(); for(Property p : i.getProperties().values()) { row.add(p.toString()); } data.add(row); } fireTableDataChanged(); } } 

Answer 1

Here is a complete example that may be useful. Since the Map sample is unmodified, I refer you to the @mKorbel example on how to override isCellEditable() and setValueAt() .

 import java.awt.EventQueue; import java.awt.GridLayout; import java.util.Map; import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.JScrollPane; import javax.swing.JTable; import javax.swing.table.AbstractTableModel; /** @see https://stackoverflow.com/questions/9132987 */ public class EnvTableTest extends JPanel { public EnvTableTest() { this.setLayout(new GridLayout()); this.add(new JScrollPane(new JTable(new EnvDataModel()))); } private static class EnvDataModel extends AbstractTableModel { private Map<String, String> data = System.getenv(); private String[] keys; public EnvDataModel() { keys = data.keySet().toArray(new String[data.size()]); } @Override public String getColumnName(int col) { if (col == 0) { return "Key"; } else { return "Value"; } } @Override public int getColumnCount() { return 2; } @Override public int getRowCount() { return data.size(); } @Override public Object getValueAt(int row, int col) { if (col == 0) { return keys[row]; } else { return data.get(keys[row]); } } } private void display() { JFrame f = new JFrame("EnvTableTest"); f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); f.add(this); f.pack(); f.setLocationRelativeTo(null); f.setVisible(true); } public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { @Override public void run() { new EnvTableTest().display(); } }); } } 

Answer 2

You can try to make the changes more atomic.

 public void populate(Collection c) { ArrayList<ArrayList<String>> data2 = new ArrayList<ArrayList<String>>(); for(Item i : c.getItems()) { ArrayList<String> row = new ArrayList<String>(); for(Property p : i.getProperties().values()) { row.add(p.toString()); } data2.add(row); } data = data2; fireTableDataChanged(); } 

I assume that populate is called again before completing the previous populate call. And, probably, c changes during its iteration.

Answer 3

1) your TableModel not complete, I skip a lot there or the required methods for JTable's life_cycle, starting with TableHeader , etc.

2), since there are many AbstactTableModels based on HashMap, I would suggest returning the type of arrays implemented directly in the API

 Vector<Vector<Object or String>> data; String[][] or Object[][] 

instead

 ArrayList<ArrayList<String>> data; 

simple explanations are that XxxList returns a column, and Vector or String [] returns a string

3) I would suggest using DefaultTableModel directly, then you will never have to solve duplicates or missing columns / rows