Display a JTable from a JComboBox

Question

When the user selects the level of difficulty of the questions to see, I want to display a `JTable1 issues by level of difficulty. There is no error, but the questions are not displayed in the table.

comboBox = new JComboBox();
comboBox.setFont(new Font("Times New Roman", Font.PLAIN, 13));
comboBox.setModel(new DefaultComboBoxModel(new String[] {
  "Afficher les questions faciles", 
  "Afficher les questions moyens", 
  "Afficher les questions difficiles"}));   

comboBox.addActionListener(new ActionListener() {
  public void actionPerformed(ActionEvent e) {
    Object selected = comboBox.getSelectedItem();
    if(selected.toString().equals("Afficher les questions faciles")) {
      questions=GestionQuestionDelegate.doFindAllQuestionsByNiveauDeDifficulte("Facile");
      System.out.println(comboBox.getSelectedItem());
    } else if(selected.toString().equals("Afficher les questions moyens")) {
      System.out.println(comboBox.getSelectedItem());
      questions=GestionQuestionDelegate.doFindAllQuestionsByNiveauDeDifficulte("Moyen");
    } else if(selected.toString().equals("Afficher les questions difficiles")) {
      System.out.println(comboBox.getSelectedItem());
      questions=GestionQuestionDelegate.doFindAllQuestionsByNiveauDeDifficulte("Difficile");
    }       
  }
});

Answer 1

There are so many aspects to your question which require more information, but basically, once you've loaded your List of questions, you simply need to wrap a TableModel around them and then apply them to the JTable you have

public class QuestionTableModel extends AbstractTableModel {
    private List<Question> questions;

    public QuestionTableModel(List<Question> questions) {
        this.questions = questions;
    }

    @Override
    public int getRowCount() {
        return questions == null ? 0 : questions.size();
    }

    @Override
    public int getColumnCount() {
        return // the number of columns you want to display
    }

    @Override
    public Class<?> getColumnClass(int columnIndex) {
        return // The object class appropriate for the column/class property 
                // you want to display
    }

    @Override
    public Object getValueAt(int rowIndex, int columnIndex) {
        Object value = null;
        if (questions != null) {
            Question question = questions.get(rowIndex);
            // Get the column value from the question
            // based on the columnIndex and the
            // question properties
        }
        return value;
    }


}

Then in your ActionListener , wrap the questions in the model and apply it to the table.

comboBox.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e) {
        Object selected = comboBox.getSelectedItem();
        if (selected.toString().equals("Afficher les questions faciles")) {
            questions = GestionQuestionDelegate.doFindAllQuestionsByNiveauDeDifficulte("Facile");
            System.out.println(comboBox.getSelectedItem());
        } else if (selected.toString().equals("Afficher les questions moyens")) {
            System.out.println(comboBox.getSelectedItem());
            questions = GestionQuestionDelegate.doFindAllQuestionsByNiveauDeDifficulte("Moyen");
        } else if (selected.toString().equals("Afficher les questions difficiles")) {
            System.out.println(comboBox.getSelectedItem());
            questions = GestionQuestionDelegate.doFindAllQuestionsByNiveauDeDifficulte("Difficile");
        }
        QuestionTableModel model = new QuestionTableModel(questions);
        table.setModel(model);
    }
});

You really need to take a look at How to Use Tables which will cover more information into how this works and what you need to do to fill out the remaining information

Answer 2

well i think the problem that you get no display is because you are printing out an object: System.out.println(comboBox.getSelectedItem()) instead of the String: System.out.println(comboBox.getSelectedItem().toString)

and i think you should use a String variable to get the output directly from the comboBox.

 if (comboBox.getSelectedIndex() != -1) {                     
           String chaine = "" 
              + comboBox.getItemAt
                (comboBox.getSelectedIndex());             
        }