InputVerifier and, using JComponent's
+ * setInputVerifier method,
+ * attach an instance of their subclass to the JComponent whose input they
+ * want to validate. Before focus is transfered to another Swing component
+ * that requests it, the input verifier's shouldYieldFocus method is
+ * called. Focus is transfered only if that method returns true.
+ * + * The following example has two text fields, with the first one expecting + * the string "pass" to be entered by the user. If that string is entered in + * the first text field, then the user can advance to the second text field + * either by clicking in it or by pressing TAB. However, if another string + * is entered in the first text field, then the user will be unable to + * transfer focus to the second text field. + *
+ *
+ * import java.awt.*;
+ * import java.util.*;
+ * import java.awt.event.*;
+ * import javax.swing.*;
+ *
+ * // This program demonstrates the use of the Swing InputVerifier class.
+ * // It creates two text fields; the first of the text fields expects the
+ * // string "pass" as input, and will allow focus to advance out of it
+ * // only after that string is typed in by the user.
+ *
+ * public class VerifierTest extends JFrame {
+ * public VerifierTest() {
+ * JTextField tf1 = new JTextField ("Type \"pass\" here");
+ * getContentPane().add (tf1, BorderLayout.NORTH);
+ * tf1.setInputVerifier(new PassVerifier());
+ *
+ * JTextField tf2 = new JTextField ("TextField2");
+ * getContentPane().add (tf2, BorderLayout.SOUTH);
+ *
+ * WindowListener l = new WindowAdapter() {
+ * public void windowClosing(WindowEvent e) {
+ * System.exit(0);
+ * }
+ * };
+ * addWindowListener(l);
+ * }
+ *
+ * class PassVerifier extends InputVerifier {
+ * public boolean verify(JComponent input) {
+ * JTextField tf = (JTextField) input;
+ * return "pass".equals(tf.getText());
+ * }
+ * }
+ *
+ * public static void main(String[] args) {
+ * Frame f = new VerifierTest();
+ * f.pack();
+ * f.setVisible(true);
+ * }
+ * }
+ *
+ *
+ * @since 1.3
+ */
+
+
+public abstract class InputVerifier {
+
+ /**
+ * Checks whether the JComponent's input is valid. This method should
+ * have no side effects. It returns a boolean indicating the status
+ * of the argument's input.
+ *
+ * @param input the JComponent to verify
+ * @return true when valid, false when invalid
+ * @see JComponent#setInputVerifier
+ * @see JComponent#getInputVerifier
+ *
+ */
+
+ public abstract boolean verify(JComponent input);
+
+
+ /**
+ * Calls verify(input) to ensure that the input is valid.
+ * This method can have side effects. In particular, this method
+ * is called when the user attempts to advance focus out of the
+ * argument component into another Swing component in this window.
+ * If this method returns true, then the focus is transfered
+ * normally; if it returns false, then the focus remains in
+ * the argument component.
+ *
+ * @param input the JComponent to verify
+ * @return true when valid, false when invalid
+ * @see JComponent#setInputVerifier
+ * @see JComponent#getInputVerifier
+ *
+ */
+
+ public boolean shouldYieldFocus(JComponent input) {
+ return verify(input);
+ }
+
+}