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How Can I Prevent Negative or Zero Values in JTable Cells?

Oct 28, 2024 pm 01:17 PM

How Can I Prevent Negative or Zero Values in JTable Cells?

Preventing Invalid Input in JTable Cells

The JTable component provides built-in validation for certain data types, such as integers. However, it does not handle negative or zero values by default. To implement custom validation rules, you can create a custom cell editor class.

Solution:

Instead of using a TableModel that validates input, create a subclass of DefaultCellEditor as follows:

<code class="java">private static class PositiveIntegerCellEditor extends DefaultCellEditor {

    private static final Border red = new LineBorder(Color.red);
    private static final Border black = new LineBorder(Color.black);
    private JTextField textField;

    public PositiveIntegerCellEditor(JTextField textField) {
        super(textField);
        this.textField = textField;
        textField.setHorizontalAlignment(JTextField.RIGHT); // Align right for positive numbers
    }

    @Override
    public boolean stopCellEditing() {
        try {
            int value = Integer.valueOf(textField.getText());
            if (value &lt; 0) {
                throw new NumberFormatException();
            }
        } catch (NumberFormatException e) {
            textField.setBorder(red); // Highlight invalid input
            return false;
        }
        textField.setBorder(black); // Reset border for valid input
        return super.stopCellEditing();
    }
}</code>

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This custom editor checks user input and displays a red border for invalid values (negative or zero).

Implementation:

Instantiate the custom editor and set it for the desired column:

<code class="java">JTextField integerField = new JTextField();
PositiveIntegerCellEditor integerEditor = new PositiveIntegerCellEditor(integerField);
table.getColumnModel().getColumn(columnIndex).setCellEditor(integerEditor);</code>

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This solution mimics the behavior of the default editor for integer input, rejecting negative or zero values and highlighting invalid cells.

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