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Tom Tromey
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libjava/classpath/gnu/java/awt/AWTUtilities.java
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libjava/classpath/gnu/java/awt/AWTUtilities.java
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/* AWTUtilities.java -- Common utility methods for AWT and Swing.
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Copyright (C) 2005 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package gnu.java.awt;
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import java.awt.Component;
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import java.awt.Container;
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import java.util.AbstractSequentialList;
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import java.util.List;
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import java.util.ListIterator;
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import java.util.NoSuchElementException;
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import java.util.WeakHashMap;
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/**
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* This class provides utility methods that are commonly used in AWT
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* (and Swing).
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*/
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public class AWTUtilities
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{
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/**
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* This List implementation wraps the Component[] returned by
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* {@link Container#getComponents()} and iterates over the visible Components
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* in that array. This class is used in {@link #getVisibleChildren}.
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*/
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static class VisibleComponentList extends AbstractSequentialList
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{
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/**
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* The ListIterator for this List.
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*/
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class VisibleComponentIterator implements ListIterator
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{
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/** The current index in the Component[]. */
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int index;
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/** The index in the List of visible Components. */
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int listIndex;
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/**
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* Creates a new VisibleComponentIterator that starts at the specified
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* <code>listIndex</code>. The array of Components is searched from
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* the beginning to find the matching array index.
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*
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* @param listIndex the index from where to begin iterating
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*/
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VisibleComponentIterator(int listIndex)
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{
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this.listIndex = listIndex;
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int visibleComponentsFound = 0;
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for (index = 0; visibleComponentsFound != listIndex; index++)
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{
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if (components[index].isVisible())
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visibleComponentsFound++;
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}
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}
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/**
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* Returns <code>true</code> if there are more visible components in the
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* array, <code>false</code> otherwise.
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*
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* @return <code>true</code> if there are more visible components in the
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* array, <code>false</code> otherwise
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*/
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public boolean hasNext()
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{
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boolean hasNext = false;
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for (int i = index; i < components.length; i++)
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{
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if (components[i].isVisible())
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{
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hasNext = true;
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break;
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}
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}
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return hasNext;
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}
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/**
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* Returns the next visible <code>Component</code> in the List.
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*
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* @return the next visible <code>Component</code> in the List
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*
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* @throws if there is no next element
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*/
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public Object next()
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{
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Object o = null;
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for (; index < components.length; index++)
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{
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if (components[index].isVisible())
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{
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o = components[index];
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break;
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}
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}
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if (o != null)
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{
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index++;
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listIndex++;
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return o;
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}
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else
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throw new NoSuchElementException();
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}
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/**
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* Returns <code>true</code> if there are more visible components in the
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* array in the reverse direction, <code>false</code> otherwise.
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*
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* @return <code>true</code> if there are more visible components in the
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* array in the reverse direction, <code>false</code> otherwise
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*/
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public boolean hasPrevious()
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{
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boolean hasPrevious = false;
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for (int i = index - 1; i >= 0; i--)
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{
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if (components[i].isVisible())
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{
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hasPrevious = true;
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break;
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}
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}
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return hasPrevious;
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}
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/**
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* Returns the previous visible <code>Component</code> in the List.
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*
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* @return the previous visible <code>Component</code> in the List
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*
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* @throws NoSuchElementException if there is no previous element
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*/
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public Object previous()
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{
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Object o = null;
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for (index--; index >= 0; index--)
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{
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if (components[index].isVisible())
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{
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o = components[index];
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break;
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}
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}
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if (o != null)
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{
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listIndex--;
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return o;
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}
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else
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throw new NoSuchElementException();
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}
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/**
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* Returns the index of the next element in the List.
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*
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* @return the index of the next element in the List
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*/
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public int nextIndex()
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{
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return listIndex + 1;
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}
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/**
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* Returns the index of the previous element in the List.
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*
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* @return the index of the previous element in the List
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*/
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public int previousIndex()
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{
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return listIndex - 1;
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}
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/**
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* This operation is not supported because the List is immutable.
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*
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* @throws UnsupportedOperationException because the List is immutable
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*/
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public void remove()
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{
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throw new UnsupportedOperationException
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("VisibleComponentList is immutable");
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}
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/**
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* This operation is not supported because the List is immutable.
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*
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* @param o not used here
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*
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* @throws UnsupportedOperationException because the List is immutable
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*/
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public void set(Object o)
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{
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throw new UnsupportedOperationException
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("VisibleComponentList is immutable");
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}
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/**
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* This operation is not supported because the List is immutable.
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*
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* @param o not used here
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*
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* @throws UnsupportedOperationException because the List is immutable
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*/
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public void add(Object o)
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{
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throw new UnsupportedOperationException
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("VisibleComponentList is immutable");
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}
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}
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/**
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* The components over which we iterate. Only the visible components
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* are returned by this List.
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*/
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Component[] components;
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/**
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* Creates a new instance of VisibleComponentList that wraps the specified
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* <code>Component[]</code>.
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*
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* @param c the <code>Component[]</code> to be wrapped.
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*/
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VisibleComponentList(Component[] c)
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{
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components = c;
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}
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/**
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* Returns a {@link ListIterator} for iterating over this List.
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*
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* @return a {@link ListIterator} for iterating over this List
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*/
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public ListIterator listIterator(int index)
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{
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return new VisibleComponentIterator(index);
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}
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/**
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* Returns the number of visible components in the wrapped Component[].
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*
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* @return the number of visible components
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*/
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public int size()
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{
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int visibleComponents = 0;
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for (int i = 0; i < components.length; i++)
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if (components[i].isVisible())
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visibleComponents++;
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return visibleComponents;
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}
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}
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/**
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* The cache for our List instances. We try to hold one instance of
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* VisibleComponentList for each Component[] that is requested. Note
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* that we use a WeakHashMap for caching, so that the cache itself
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* does not keep the array or the List from beeing garbage collected
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* if no other objects hold references to it.
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*/
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static WeakHashMap visibleChildrenCache = new WeakHashMap();
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/**
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* Returns the visible children of a {@link Container}. This method is
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* commonly needed in LayoutManagers, because they only have to layout
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* the visible children of a Container.
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*
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* @param c the Container from which to extract the visible children
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*
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* @return the visible children of <code>c</code>
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*/
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public static List getVisibleChildren(Container c)
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{
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Component[] children = c.getComponents();
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Object o = visibleChildrenCache.get(children);
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VisibleComponentList visibleChildren = null;
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if (o == null)
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{
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visibleChildren = new VisibleComponentList(children);
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visibleChildrenCache.put(children, visibleChildren);
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}
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else
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visibleChildren = (VisibleComponentList) o;
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return visibleChildren;
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}
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}
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