001    /* InputVerifier.java --
002       Copyright (C) 2002, 2004 Free Software Foundation, Inc.
003    
004    This file is part of GNU Classpath.
005    
006    GNU Classpath is free software; you can redistribute it and/or modify
007    it under the terms of the GNU General Public License as published by
008    the Free Software Foundation; either version 2, or (at your option)
009    any later version.
010    
011    GNU Classpath is distributed in the hope that it will be useful, but
012    WITHOUT ANY WARRANTY; without even the implied warranty of
013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014    General Public License for more details.
015    
016    You should have received a copy of the GNU General Public License
017    along with GNU Classpath; see the file COPYING.  If not, write to the
018    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019    02110-1301 USA.
020    
021    Linking this library statically or dynamically with other modules is
022    making a combined work based on this library.  Thus, the terms and
023    conditions of the GNU General Public License cover the whole
024    combination.
025    
026    As a special exception, the copyright holders of this library give you
027    permission to link this library with independent modules to produce an
028    executable, regardless of the license terms of these independent
029    modules, and to copy and distribute the resulting executable under
030    terms of your choice, provided that you also meet, for each linked
031    independent module, the terms and conditions of the license of that
032    module.  An independent module is a module which is not derived from
033    or based on this library.  If you modify this library, you may extend
034    this exception to your version of the library, but you are not
035    obligated to do so.  If you do not wish to do so, delete this
036    exception statement from your version. */
037    
038    package javax.swing;
039    
040    
041    /**
042     * Verifies the user input on a component before the focus is shifted.
043     * It is sometimes necessary that input components have a valid state before
044     * they loose focus. Such components can have a <code>InputVerifier</code>
045     * subclass registered, that permits or vetos a focus change request.
046     *
047     * @author Andrew Selkirk
048     */
049    public abstract class InputVerifier
050    {
051      /**
052       * Creates a <code>InputVerifier</code>
053       */
054      public InputVerifier()
055      {
056        // Nothing to do here.
057      }
058    
059      /**
060       * verify
061       *
062       * @param component the component to verify
063       *
064       * @return <code>true</code> if valid, <code>false</code> otherwise.
065       */
066      public abstract boolean verify(JComponent component);
067    
068      /**
069       * shouldYieldFocus
070       *
071       * @param component the component to verify
072       *
073       * @return <code>true</code> if valid, <code>false</code> otherwise.
074       */
075      public boolean shouldYieldFocus(JComponent component)
076      {
077        return verify(component);
078      }
079    }