Cercare di migliorarne il funzionamento eliminando i bachi…
package inputnumerico; import java.awt.event.KeyEvent; import java.awt.event.KeyListener; import javax.swing.JTextField; public class JNumberField extends JTextField implements KeyListener { private String oldText = "0"; private double n = 0; public JNumberField() { this.setText("0"); this.setColumns(10); this.addKeyListener(this); } public double getN() { return n; } public void setN(double n) { this.n = n; } @Override public void keyTyped(KeyEvent ke) { } @Override public void keyPressed(KeyEvent ke) { } @Override public void keyReleased(KeyEvent ke) { try { String newText = this.getText(); n = Double.parseDouble(newText); oldText = newText; } catch (NumberFormatException numberFormatException) { this.setText(oldText); } } }