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1   /*
2    * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4    *
5    * This code is free software; you can redistribute it and/or modify it
6    * under the terms of the GNU General Public License version 2 only, as
7    * published by the Free Software Foundation.  Oracle designates this
8    * particular file as subject to the "Classpath" exception as provided
9    * by Oracle in the LICENSE file that accompanied this code.
10   *
11   * This code is distributed in the hope that it will be useful, but WITHOUT
12   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14   * version 2 for more details (a copy is included in the LICENSE file that
15   * accompanied this code).
16   *
17   * You should have received a copy of the GNU General Public License version
18   * 2 along with this work; if not, write to the Free Software Foundation,
19   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20   *
21   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22   * or visit www.oracle.com if you need additional information or have any
23   * questions.
24   */
25  
26  package javax.swing;
27  
28  import java.util.*;
29  
30  /**
31   * The purpose of this class is to help clients support smooth focus
32   * navigation through GUIs with text fields. Such GUIs often need
33   * to ensure that the text entered by the user is valid (for example,
34   * that it's in
35   * the proper format) before allowing the user to navigate out of
36   * the text field. To do this, clients create a subclass of
37   * <code>InputVerifier</code> and, using <code>JComponent</code>'s
38   * <code>setInputVerifier</code> method,
39   * attach an instance of their subclass to the <code>JComponent</code> whose input they
40   * want to validate. Before focus is transfered to another Swing component
41   * that requests it, the input verifier's <code>shouldYieldFocus</code> method is
42   * called.  Focus is transfered only if that method returns <code>true</code>.
43   * <p>
44   * The following example has two text fields, with the first one expecting
45   * the string "pass" to be entered by the user. If that string is entered in
46   * the first text field, then the user can advance to the second text field
47   * either by clicking in it or by pressing TAB. However, if another string
48   * is entered in the first text field, then the user will be unable to
49   * transfer focus to the second text field.
50   *
51   * <pre>
52   * import java.awt.*;
53   * import java.util.*;
54   * import java.awt.event.*;
55   * import javax.swing.*;
56   *
57   * // This program demonstrates the use of the Swing InputVerifier class.
58   * // It creates two text fields; the first of the text fields expects the
59   * // string "pass" as input, and will allow focus to advance out of it
60   * // only after that string is typed in by the user.
61   *
62   * public class VerifierTest extends JFrame {
63   *     public VerifierTest() {
64   *         JTextField tf1 = new JTextField ("Type \"pass\" here");
65   *         getContentPane().add (tf1, BorderLayout.NORTH);
66   *         tf1.setInputVerifier(new PassVerifier());
67   *
68   *         JTextField tf2 = new JTextField ("TextField2");
69   *         getContentPane().add (tf2, BorderLayout.SOUTH);
70   *
71   *         WindowListener l = new WindowAdapter() {
72   *             public void windowClosing(WindowEvent e) {
73   *                 System.exit(0);
74   *             }
75   *         };
76   *         addWindowListener(l);
77   *     }
78   *
79   *     class PassVerifier extends InputVerifier {
80   *         public boolean verify(JComponent input) {
81   *             JTextField tf = (JTextField) input;
82   *             return "pass".equals(tf.getText());
83   *         }
84   *     }
85   *
86   *     public static void main(String[] args) {
87   *         Frame f = new VerifierTest();
88   *         f.pack();
89   *         f.setVisible(true);
90   *     }
91   * }
92   * </pre>
93   *
94   *  @since 1.3
95   */
96  
97  
98  public abstract class InputVerifier {
99  
100   /**
101    * Checks whether the JComponent's input is valid. This method should
102    * have no side effects. It returns a boolean indicating the status
103    * of the argument's input.
104    *
105    * @param input the JComponent to verify
106    * @return <code>true</code> when valid, <code>false</code> when invalid
107    * @see JComponent#setInputVerifier
108    * @see JComponent#getInputVerifier
109    *
110    */
111 
112   public abstract boolean verify(JComponent input);
113 
114 
115   /**
116    * Calls <code>verify(input)</code> to ensure that the input is valid.
117    * This method can have side effects. In particular, this method
118    * is called when the user attempts to advance focus out of the
119    * argument component into another Swing component in this window.
120    * If this method returns <code>true</code>, then the focus is transfered
121    * normally; if it returns <code>false</code>, then the focus remains in
122    * the argument component.
123    *
124    * @param input the JComponent to verify
125    * @return <code>true</code> when valid, <code>false</code> when invalid
126    * @see JComponent#setInputVerifier
127    * @see JComponent#getInputVerifier
128    *
129    */
130 
131   public boolean shouldYieldFocus(JComponent input) {
132     return verify(input);
133   }
134 
135 }