/*
 * @(#)SpinnerModel.java	1.3 01/12/03
 *
 * Copyright 2002 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package javax.swing;

import java.awt.event.*;
import javax.swing.event.*;


/**
 * A model for a potentially unbounded sequence of object values.  This model
 * is similar to <code>ListModel</code> however there are some important differences:
 * <ul>
 * <li> The number of sequence elements isn't neccessarily bounded.
 * <li> The model doesn't support indexed random access to sequence elements.
 *      Only three sequence values are accessible at a time: current, next and
 *      previous.
 * <li> The current sequence element, can be set.
 * </ul>
 * <p>
 * A <code>SpinnerModel</code> has three properties, only the first is read/write.
 * <dl>
 *   <dt><code>value</code>
 *   <dd>The current element of the sequence.  
 * 
 *   <dt><code>nextValue</code>
 *   <dd>The following element or null if <code>value</code> is the 
 *     last element of the sequence.
 * 
 *   <dt><code>previousValue</code>
 *   <dd>The preceeding element or null if <code>value</code> is the 
 *     first element of the sequence.
 * </dl>
 * When the the <code>value</code> property changes, 
 * <code>ChangeListeners</code> are notified.  <code>SpinnerModel</code> may
 * choose to notify the <code>ChangeListeners</code> under other circumstances.
 * 
 * @see JSpinner
 * @see AbstractSpinnerModel
 * @see SpinnerListodel
 * @see SpinnerNumberModel
 * @see SpinnerDateModel
 * 
 * @version 1.3 12/03/01
 * @author Hans Muller
 * @since 1.4
 */
public interface SpinnerModel 
{
    /**
     * The <i>current element</i> of the sequence.  This element is usually
     * displayed by the <code>editor</code> part of a <code>JSpinner</code>.
     * 
     * @return the current spinner value.
     * @see #setValue
     */
    Object getValue();


    /**
     * Changes current value of the model, typically this value is displayed 
     * by the <code>editor</code> part of a  <code>JSpinner</code>.  
     * If the <code>SpinnerModel</code> implementation doesn't support 
     * the specified value then an <code>IllegalArgumentException</code> 
     * is thrown.  For example a <code>SpinnerModel</code> for numbers might 
     * only support values that are integer multiples of ten. In
     * that case, <code>model.setValue(new Number(11))</code>
     * would throw an exception.
     * 
     * @throws IllegalArgumentException if <code>value</code> isn't allowed
     * @see #getValue
     */
    void setValue(Object value);


    /**
     * Return the object in the sequence that comes after the object returned 
     * by <code>getValue()</code>. If the end of the sequence has been reached 
     * then return null.  Calling this method does not effect <code>value</code>.
     * 
     * @return the next legal value or null if one doesn't exist
     * @see #getValue
     * @see #getPreviousValue
     */
    Object getNextValue();


    /**
     * Return the object in the sequence that comes before the object returned 
     * by <code>getValue()</code>.  If the end of the sequence has been reached then 
     * return null. Calling this method does not effect <code>value</code>.
     * 
     * @return the previous legal value or null if one doesn't exist
     * @see #getValue
     * @see #getNextValue
     */
    Object getPreviousValue();


    /**
     * Adds a <code>ChangeListener</code> to the model's listener list.  The 
     * <code>ChangeListeners</code> must be notified when models <code>value</code> 
     * changes.
     *
     * @param l the ChangeListener to add
     * @see #removeChangeListener
     */
    void addChangeListener(ChangeListener l);


    /**
     * Removes a <code>ChangeListener</code> from the model's listener list.
     *
     * @param l the ChangeListener to remove
     * @see #addChangeListener
     */
    void removeChangeListener(ChangeListener l);
}
