Java tutorial
import java.awt.BorderLayout; import java.awt.Color; import java.awt.Font; import java.awt.font.TextAttribute; import java.math.RoundingMode; import java.text.DecimalFormat; import java.text.NumberFormat; import java.util.Map; import javax.swing.JFormattedTextField; import javax.swing.JFormattedTextField.AbstractFormatter; import javax.swing.JFormattedTextField.AbstractFormatterFactory; import javax.swing.JFrame; import javax.swing.event.DocumentEvent; import javax.swing.event.DocumentListener; import javax.swing.text.InternationalFormatter; public class Main { public static void main(String args[]) { JFrame frame = new JFrame(); final JFormattedTextField textField1 = new JFormattedTextField(new Float(10.01)); textField1.setFormatterFactory(new AbstractFormatterFactory() { @Override public AbstractFormatter getFormatter(JFormattedTextField tf) { NumberFormat format = DecimalFormat.getInstance(); format.setMinimumFractionDigits(2); format.setMaximumFractionDigits(2); format.setRoundingMode(RoundingMode.HALF_UP); InternationalFormatter formatter = new InternationalFormatter(format); formatter.setAllowsInvalid(false); formatter.setMinimum(0.0); formatter.setMaximum(1000.00); return formatter; } }); Map attributes = (new Font("Serif", Font.BOLD, 16)).getAttributes(); attributes.put(TextAttribute.STRIKETHROUGH, TextAttribute.STRIKETHROUGH_ON); final JFormattedTextField textField2 = new JFormattedTextField(new Float(10.01)); textField2.setFormatterFactory(new AbstractFormatterFactory() { @Override public AbstractFormatter getFormatter(JFormattedTextField tf) { NumberFormat format = DecimalFormat.getInstance(); format.setMinimumFractionDigits(2); format.setMaximumFractionDigits(2); format.setRoundingMode(RoundingMode.HALF_UP); InternationalFormatter formatter = new InternationalFormatter(format); formatter.setAllowsInvalid(false); formatter.setMinimum(0.0); formatter.setMaximum(1000.00); return formatter; } }); textField2.getDocument().addDocumentListener(new DocumentListener() { @Override public void changedUpdate(DocumentEvent documentEvent) { printIt(documentEvent); } @Override public void insertUpdate(DocumentEvent documentEvent) { printIt(documentEvent); } @Override public void removeUpdate(DocumentEvent documentEvent) { printIt(documentEvent); } private void printIt(DocumentEvent documentEvent) { DocumentEvent.EventType type = documentEvent.getType(); double t1a1 = (((Number) textField2.getValue()).doubleValue()); if (t1a1 > 100) { textField2.setFont(new Font(attributes)); textField2.setForeground(Color.red); } else { textField2.setFont(new Font("Serif", Font.BOLD, 16)); textField2.setForeground(Color.black); } } }); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.add(textField1, BorderLayout.NORTH); frame.add(textField2, BorderLayout.SOUTH); frame.setVisible(true); frame.pack(); } }