Java: Table with numeric input and length checks

Sample code showing how to do numeric input and character length checks with a JTable:

	/*
	* Table with numeric input and length checks.
	* Şamil Korkmaz, June 2022
	*/
	package tablewithnumericinput;
	import java.awt.Color;
	import java.awt.event.KeyEvent;
	import java.awt.event.KeyListener;
	import javax.swing.DefaultCellEditor;
	import javax.swing.InputVerifier;
	import javax.swing.JButton;
	import javax.swing.JComponent;
	import javax.swing.JFrame;
	import javax.swing.JOptionPane;
	import javax.swing.JScrollPane;
	import javax.swing.JTable;
	import javax.swing.JTextField;
	import javax.swing.table.DefaultTableModel;
	public class TableWithNumericInput {
	static private JTextField jtfForNumericFields;
	static class MyKeyListener implements KeyListener {
	@Override
	public void keyTyped(KeyEvent ke) {
	if (ke.getKeyCode() != KeyEvent.VK_BACK_SPACE && ke.getKeyCode() != KeyEvent.VK_DELETE) {
	char c = ke.getKeyChar();
	System.out.println("c = " + c);
	System.out.println("Inside keyTyped()");
	if (ke.getSource() instanceof JTextField) { //When user first double clicks on table and then presses a key, jtf will be the key event source
	System.out.println("Key event source is text field");
	} else if (ke.getSource() instanceof JTable) { //When table has focus but user has not double clicked on it, table will be the key event source
	System.out.println("Key event source is table");
	}
	try {
	Double.parseDouble(jtfForNumericFields.getText() + c); //getText() returns text before keypress, we have to add pressed key char to get full text
	if (c == 'd' || c == 'f') { //parseDouble accepts 'd' and 'f' at the end of text
	ke.consume(); //ignore key press
	} else {
	if (!jtfForNumericFields.getInputVerifier().verify(jtfForNumericFields)) { //check if text exceeds max nb of characters
	ke.consume(); //ignore key press
	}
	}
	} catch (NumberFormatException e) { //text is not a number
	ke.consume(); //ignore key press
	}
	}
	}
	@Override
	public void keyPressed(KeyEvent ke) {
	}
	@Override
	public void keyReleased(KeyEvent ke) {
	}
	}
	static class MyTable extends JTable {
	public MyTable() {
	putClientProperty("terminateEditOnFocusLost", true); //To make sure that setValue() is called when user clicks on another component, e.g. a button.
	}
	@Override
	public void setValueAt(Object value, int iRow, int iColumn) {
	if (value != null && ((String)value).length() > 0) {
	if (iColumn > 0) {
	double doubleValue = Double.parseDouble((String)value);
	super.setValueAt(doubleValue, iRow, iColumn);
	} else {
	super.setValueAt(value, iRow, iColumn);
	}
	}
	}
	}
	public static void main(String[] args) {
	JFrame jf = new JFrame();
	jf.setTitle("Table with numeric input checks");
	jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	jf.getContentPane().setLayout(new javax.swing.BoxLayout(jf.getContentPane(), javax.swing.BoxLayout.PAGE_AXIS));
	JTable jt = new MyTable();
	jf.add(new JScrollPane(jt)); //to show table column headers
	JButton jb = new JButton("OK");
	jb.addActionListener((java.awt.event.ActionEvent evt) -> {
	JOptionPane.showMessageDialog(jf, "Table contents: " + jt.getValueAt(0, 0) + ", " + jt.getValueAt(0, 1));
	});
	jf.add(jb);
	jf.setBounds(100, 100, 400, 150);
	jt.setBorder(javax.swing.BorderFactory.createLineBorder(Color.BLACK));
	DefaultTableModel model = new DefaultTableModel() {
	Class[] types = new Class[]{String.class, Double.class};
	@Override
	public Class getColumnClass(int iCol) {
	return types[iCol];
	}
	};
	jt.setModel(model);
	model.addColumn("ID");
	model.addColumn("Double Value");
	model.addRow(new Object[]{});
	final int PANEL_WIDTH = 200;
	final int TABLE_HEIGHT = 3 * jt.getRowHeight();
	jt.setBounds(0, jt.getRowHeight(), PANEL_WIDTH, TABLE_HEIGHT);
	jt.getTableHeader().setBounds(0, 0, PANEL_WIDTH, jt.getRowHeight());
	jtfForNumericFields = new JTextField();
	jtfForNumericFields.setInputVerifier(new InputVerifier() {
	@Override
	public boolean verify(JComponent jc) {
	JTextField jtf = (JTextField) jc;
	String text = jtf.getText();
	System.out.println("Text: " + text);
	final int maxLength = 9;
	if (text.length() > (maxLength - 1)) {
	System.out.println("length > " + maxLength);
	return false;
	}
	return true;
	}
	});
	//Note that we have to add key listener to both table and text field because when
	//table column 1 has focus and user presses a key, editing will start and table will catch
	//key events. If user double click on column 1, then text field will catch key events:
	jt.addKeyListener(new MyKeyListener());
	jtfForNumericFields.addKeyListener(new MyKeyListener());
	//Use numeric text field as editor for column 1 (second column):
	jt.getColumnModel().getColumn(1).setCellEditor(new DefaultCellEditor(jtfForNumericFields));
	jf.setVisible(true);
	}
	}

view raw TableWithNumericInput.java hosted with ❤ by GitHub