As pointed out by one Mauve test, the SimpleAttributeSet.EMPTY field
shouldn't be of the type SimpleAttributeSet, because, in theory, an
application could cast to SimpleAttributeSet then and modify this
object. I implemented an immutable empty AttributeSet class, which is
now used for this field.
2006-07-27 Roman Kennke <[EMAIL PROTECTED]>
* javax/swing/text/SimpleAttributeSet.java
(EMPTY): Use EmptyAttributeSet for this field rather than
SimpleAttributeSet.
* javax/swing/text/EmptyAttributeSet.java: New class. Implements
an empty and immutable AttributeSet.
/Roman
Index: javax/swing/text/SimpleAttributeSet.java
===================================================================
RCS file: /cvsroot/classpath/classpath/javax/swing/text/SimpleAttributeSet.java,v
retrieving revision 1.14
diff -u -1 -2 -r1.14 SimpleAttributeSet.java
--- javax/swing/text/SimpleAttributeSet.java 16 Jan 2006 10:00:26 -0000 1.14
+++ javax/swing/text/SimpleAttributeSet.java 27 Jul 2006 14:36:30 -0000
@@ -42,26 +42,28 @@
import java.util.Enumeration;
import java.util.Hashtable;
/**
* A set of attributes.
*/
public class SimpleAttributeSet
implements MutableAttributeSet, Serializable, Cloneable
{
/** The serialization UID (compatible with JDK1.5). */
private static final long serialVersionUID = 8267656273837665219L;
- /** An empty attribute set. */
- public static final AttributeSet EMPTY = new SimpleAttributeSet();
+ /**
+ * An empty attribute set.
+ */
+ public static final AttributeSet EMPTY = new EmptyAttributeSet();
/** Storage for the attributes. */
Hashtable tab;
/**
* Creates a new attribute set that is initially empty.
*/
public SimpleAttributeSet()
{
tab = new Hashtable();
}
Index: javax/swing/text/EmptyAttributeSet.java
===================================================================
RCS file: javax/swing/text/EmptyAttributeSet.java
diff -N javax/swing/text/EmptyAttributeSet.java
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ javax/swing/text/EmptyAttributeSet.java 27 Jul 2006 14:36:30 -0000
@@ -0,0 +1,153 @@
+/* EmptyAttributeSet.java -- An empty attribute set
+ Copyright (C) 2006 Free Software Foundation, Inc.
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+GNU Classpath 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 for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING. If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library. Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module. An independent module is a module which is not derived from
+or based on this library. If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so. If you do not wish to do so, delete this
+exception statement from your version. */
+
+
+package javax.swing.text;
+
+import java.util.Enumeration;
+import java.util.NoSuchElementException;
+
+/**
+ * An immutable, empty attribute set.
+ *
+ * @see SimpleAttributeSet#EMPTY
+ *
+ * @author Roman Kennke ([EMAIL PROTECTED])
+ */
+final class EmptyAttributeSet
+ implements AttributeSet
+{
+
+ /**
+ * Always return false as this AttributeSet doesn't contain any attributes.
+ */
+ public boolean containsAttribute(Object name, Object value)
+ {
+ return false;
+ }
+
+ /**
+ * Return true only if the attributes argument also contains no attributes.
+ */
+ public boolean containsAttributes(AttributeSet attributes)
+ {
+ return attributes.getAttributeCount() == 0;
+ }
+
+ /**
+ * Return this, as this is immutable.
+ */
+ public AttributeSet copyAttributes()
+ {
+ return this;
+ }
+
+ /**
+ * Always return null as this AttributeSet doesn't contain any attributes.
+ */
+ public Object getAttribute(Object key)
+ {
+ return null;
+ }
+
+ /**
+ * Always return 0.
+ */
+ public int getAttributeCount()
+ {
+ return 0;
+ }
+
+ /**
+ * Returns an empty Enumeration.
+ */
+ public Enumeration getAttributeNames()
+ {
+ return new Enumeration()
+ {
+ public boolean hasMoreElements()
+ {
+ return false;
+ }
+
+ public Object nextElement()
+ {
+ throw new NoSuchElementException("No more elements");
+ }
+
+ };
+ }
+
+ /**
+ * Always return null as this has no resolve parent.
+ */
+ public AttributeSet getResolveParent()
+ {
+ return null;
+ }
+
+ /**
+ * Always return false as this AttributeSet doesn't contain any attributes.
+ */
+ public boolean isDefined(Object attrName)
+ {
+ return false;
+ }
+
+ /**
+ * Other attribute sets are equal if they are empty too.
+ */
+ public boolean isEqual(AttributeSet attr)
+ {
+ return attr.getAttributeCount() == 0;
+ }
+
+ /**
+ * Other objects are equal if it's the same instance as this, or if
+ * it's another attribute set without attributes.
+ */
+ public boolean equals(Object o)
+ {
+ boolean eq = o == this;
+ if (! eq)
+ {
+ eq = (o instanceof AttributeSet)
+ && ((AttributeSet) o).getAttributeCount() == 0;
+ }
+ return eq;
+ }
+}
