/*
 * Copyright (c) 1996, 2013, 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 java.awt.event;

import java.util.EventListener;

The listener interface for receiving keyboard focus events on a component. The class that is interested in processing a focus event either implements this interface (and all the methods it contains) or extends the abstract FocusAdapter class (overriding only the methods of interest). The listener object created from that class is then registered with a component using the component's addFocusListener method. When the component gains or loses the keyboard focus, the relevant method in the listener object is invoked, and the FocusEvent is passed to it. 
Author:
Carl Quinn
See Also:
FocusAdapter
FocusEvent
Tutorial: Writing a Focus Listener
Since:
1.1/**
 * The listener interface for receiving keyboard focus events on
 * a component.
 * The class that is interested in processing a focus event
 * either implements this interface (and all the methods it
 * contains) or extends the abstract {@code FocusAdapter} class
 * (overriding only the methods of interest).
 * The listener object created from that class is then registered with a
 * component using the component's {@code addFocusListener}
 * method. When the component gains or loses the keyboard focus,
 * the relevant method in the listener object
 * is invoked, and the {@code FocusEvent} is passed to it.
 *
 * @see FocusAdapter
 * @see FocusEvent
 * @see <a href="https://docs.oracle.com/javase/tutorial/uiswing/events/focuslistener.html">Tutorial: Writing a Focus Listener</a>
 *
 * @author Carl Quinn
 * @since 1.1
 */
public interface FocusListener extends EventListener {

    
Invoked when a component gains the keyboard focus.
Params:
e – the event to be processed/**
     * Invoked when a component gains the keyboard focus.
     * @param e the event to be processed
     */
    public void focusGained(FocusEvent e);

    
Invoked when a component loses the keyboard focus.
Params:
e – the event to be processed/**
     * Invoked when a component loses the keyboard focus.
     * @param e the event to be processed
     */
    public void focusLost(FocusEvent e);
}