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154 lines
3.9 KiB
Java
154 lines
3.9 KiB
Java
/* EmptyAttributeSet.java -- An empty attribute set
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Copyright (C) 2006 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 javax.swing.text;
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import java.util.Enumeration;
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import java.util.NoSuchElementException;
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/**
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* An immutable, empty attribute set.
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*
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* @see SimpleAttributeSet#EMPTY
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*
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* @author Roman Kennke (kennke@aicas.com)
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*/
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final class EmptyAttributeSet
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implements AttributeSet
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{
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/**
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* Always return false as this AttributeSet doesn't contain any attributes.
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*/
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public boolean containsAttribute(Object name, Object value)
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{
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return false;
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}
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/**
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* Return true only if the attributes argument also contains no attributes.
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*/
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public boolean containsAttributes(AttributeSet attributes)
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{
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return attributes.getAttributeCount() == 0;
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}
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/**
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* Return this, as this is immutable.
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*/
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public AttributeSet copyAttributes()
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{
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return this;
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}
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/**
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* Always return null as this AttributeSet doesn't contain any attributes.
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*/
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public Object getAttribute(Object key)
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{
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return null;
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}
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/**
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* Always return 0.
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*/
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public int getAttributeCount()
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{
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return 0;
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}
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/**
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* Returns an empty Enumeration.
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*/
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public Enumeration getAttributeNames()
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{
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return new Enumeration()
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{
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public boolean hasMoreElements()
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{
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return false;
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}
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public Object nextElement()
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{
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throw new NoSuchElementException("No more elements");
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}
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};
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}
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/**
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* Always return null as this has no resolve parent.
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*/
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public AttributeSet getResolveParent()
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{
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return null;
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}
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/**
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* Always return false as this AttributeSet doesn't contain any attributes.
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*/
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public boolean isDefined(Object attrName)
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{
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return false;
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}
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/**
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* Other attribute sets are equal if they are empty too.
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*/
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public boolean isEqual(AttributeSet attr)
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{
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return attr.getAttributeCount() == 0;
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}
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/**
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* Other objects are equal if it's the same instance as this, or if
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* it's another attribute set without attributes.
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*/
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public boolean equals(Object o)
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{
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boolean eq = o == this;
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if (! eq)
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{
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eq = (o instanceof AttributeSet)
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&& ((AttributeSet) o).getAttributeCount() == 0;
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}
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return eq;
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}
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}
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