On Tue, Jan 09, 2001 at 11:59:17PM +0100, Mark Wielaard wrote:
>
> * gnu/java/util/DoubleEnumeration.java: new class, adapted from
> java.util.DoubleEnumeration. Clears references earlier, handles null
> and/or empty enumerations better.
> * gnu/java/util/EmptyEnumeration.java: new class.
Forgot the diff. Here it is.
Cheers,
Mark
Index: java/util/DoubleEnumeration.java
===================================================================
RCS file: /cvs/classpath/java/util/DoubleEnumeration.java,v
retrieving revision 1.5
diff -u -r1.5 DoubleEnumeration.java
--- java/util/DoubleEnumeration.java 2000/10/26 10:19:00 1.5
+++ java/util/DoubleEnumeration.java 2001/01/09 22:46:49
@@ -1,5 +1,5 @@
-/* java.util.DoubleEnumeration
- Copyright (C) 1998, 1999 Free Software Foundation, Inc.
+/* gnu.java.util.DoubleEnumeration
+ Copyright (C) 1998, 1999, 2001 Free Software Foundation, Inc.
This file is part of GNU Classpath.
@@ -24,57 +24,68 @@
This exception does not however invalidate any other reasons why the
executable file might be covered by the GNU General Public License. */
+package gnu.java.util;
-package java.util;
import java.io.*;
+import java.util.Enumeration;
+import java.util.NoSuchElementException;
+
/**
- * This is a package private class that combines two Enumerations.
+ * This is a helper class that combines two Enumerations.
* It returns the elements of the first Enumeration until it has
* no more elements and then returns the elements of the second
* Enumeration.<br>
*
* In the default case:
* <pre>
+ * doubleEnum = new DoubleEnumeration(enum1, enum2);
* while (doubleEnum.hasMoreElements()) {
* Object o = doubleEnum.nextElement();
* do_something(o);
* }
* </pre>
- * it calls hasMoreElements of the first Enumeration as few times as
+ * it calls hasMoreElements of the Enumerations as few times as
* possible.
+ * The references to the Enumerations are cleared as soon as they have no
+ * more elements to help garbage collecting.
*
- * @author Jochen Hoenicke */
-class DoubleEnumeration implements Enumeration
+ * @author Jochen Hoenicke
+ * @author Mark Wielaard ([EMAIL PROTECTED])
+ */
+public class DoubleEnumeration implements Enumeration
{
/**
- * This is true as long as the first enumeration may have more
+ * This is true as long as one of the enumerations has more
* elements.
+ * Only valid when hasChecked is true.
+ * Set in <code>hasMoreElements()</code>
*/
- boolean hasMore;
+ private boolean hasMore;
/**
- * This is true, if it is sure that the first enumeration has
+ * This is true, if it is sure that hasMore indicates wether there are
* more elements.
+ * Set to true in <code>hasMoreElements()</code>.
+ * Set to false in <code>getNextElement()</code>.
*/
- boolean hasChecked;
+ private boolean hasChecked;
/**
* The first enumeration.
*/
- Enumeration e1;
+ private Enumeration e1;
/**
* The second enumeration.
*/
- Enumeration e2;
+ private Enumeration e2;
/**
* Creates a new Enumeration combining the given two enumerations.
* The enumerations mustn't be accessed by other classes.
*/
- DoubleEnumeration(Enumeration e1, Enumeration e2)
+ public DoubleEnumeration(Enumeration e1, Enumeration e2)
{
this.e1 = e1;
this.e2 = e2;
- hasMore = true;
hasChecked = false;
}
@@ -84,21 +95,34 @@
*/
public boolean hasMoreElements()
{
- if (hasMore)
- hasChecked = hasMore = e1.hasMoreElements();
- return hasMore ? true : e2.hasMoreElements();
+ if (hasChecked)
+ return hasMore;
+
+ hasMore = (e1 != null && e1.hasMoreElements());
+
+ if (!hasMore) {
+ e1 = e2;
+ e2 = null;
+ hasMore = (e1 != null && e1.hasMoreElements());
+ }
+
+ hasChecked = true;
+ return hasMore;
}
/**
* Returns the next element. This returns the next element of the
* first enumeration, if it has more elements, otherwise the next
- * element of the second enumeration.
+ * element of the second enumeration. If both enumeration don't have
+ * any elements it throws a <code>NoSuchElementException</code>.
*/
public Object nextElement()
{
- if (hasMore && !hasChecked)
- hasMore = e1.hasMoreElements();
- hasChecked = false;
- return hasMore ? e1.nextElement() : e2.nextElement();
+ if (!hasMoreElements())
+ throw new NoSuchElementException();
+ else {
+ hasChecked = false;
+ return e1.nextElement();
+ }
}
}
/* gnu.java.util.EmptyEnumeration
Copyright (C) 2001 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., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.
As a special exception, if you link this library with other files to
produce an executable, this library does not by itself cause the
resulting executable to be covered by the GNU General Public License.
This exception does not however invalidate any other reasons why the
executable file might be covered by the GNU General Public License. */
package gnu.java.util;
import java.util.Enumeration;
import java.util.NoSuchElementException;
/**
* This is a helper class that produces an empty Enumerations.
* There is only one instance of this class that can be used whenever one
* needs a non-null but empty enumeration. Using this class prevents multiple
* small objects and inner classes. <code>getInstance()</code> returns
* the only instance of this class. It can be shared by multiple objects and
* threads
* <p>
* <code>hasMoreElements()</code> always returns <code>false</code>.
* <code>nextElement()</code> always throws <code>NoSuchElementException</code>.
*
* @author Mark Wielaard ([EMAIL PROTECTED])
*/
public final class EmptyEnumeration implements Enumeration {
/** The only instance of this class */
private static final EmptyEnumeration instance = new EmptyEnumeration();
/**
* Private constructor that creates a new empty Enumeration.
*/
private EmptyEnumeration() {
}
/**
* Returns the only instance of this class.
* It can be shared by multiple objects and threads.
*/
public static EmptyEnumeration getInstance() {
return instance;
}
/**
* Always returns <code>false</code>.
*/
public boolean hasMoreElements() {
return false;
}
/**
* Always throws <code>NoSuchElementException</code>.
*/
public Object nextElement() throws NoSuchElementException {
throw new NoSuchElementException();
}
}
