/* * Copyright (c) 1999, 2000, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation.  Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package javax.swing; import java.util.*; /** * The purpose of this class is to help clients support smooth focus * navigation through GUIs with text fields. Such GUIs often need * to ensure that the text entered by the user is valid (for example, * that it's in * the proper format) before allowing the user to navigate out of * the text field. To do this, clients create a subclass of * <code>InputVerifier</code> and, using <code>JComponent</code>'s * <code>setInputVerifier</code> method, * attach an instance of their subclass to the <code>JComponent</code> whose input they * want to validate. Before focus is transfered to another Swing component * that requests it, the input verifier's <code>shouldYieldFocus</code> method is * called.  Focus is transfered only if that method returns <code>true</code>. * <p> * 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. * <p> * <pre> * 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); *     } * } * </pre> * *  @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 <code>true</code> when valid, <code>false</code> when invalid   * @see JComponent#setInputVerifier   * @see JComponent#getInputVerifier   *   */   public abstract boolean verify(JComponent input);    /**   * Calls <code>verify(input)</code> 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 <code>true</code>, then the focus is transfered   * normally; if it returns <code>false</code>, then the focus remains in   * the argument component.   *   * @param input the JComponent to verify   * @return <code>true</code> when valid, <code>false</code> when invalid   * @see JComponent#setInputVerifier   * @see JComponent#getInputVerifier   *   */   public boolean shouldYieldFocus(JComponent input) {    return verify(input);  } }