From 3831381763ca5f41d6f7406d590e1e38a8531e1c Mon Sep 17 00:00:00 2001 From: Tom Tromey Date: Tue, 18 Jun 2002 15:40:16 +0000 Subject: javaprims.h: Updated class declaration list. * gcj/javaprims.h: Updated class declaration list. * Makefile.in: Rebuilt. * Makefile.am (core_java_source_files): Added PropertyPermissionCollection.java. * java/lang/Thread.java (group, name): Now package-private. * java/lang/ThreadGroup.java: Re-merge with Classpath. * java/util/AbstractList.java: Likewise. * java/util/AbstractMap.java: Likewise. * java/util/Calendar.java: Likewise. * java/util/Collections.java: Likewise. * java/util/HashMap.java: Likewise. * java/util/Hashtable.java: Likewise. * java/util/LinkedHashMap.java: Likewise. * java/util/LinkedList.java: Likewise. * java/util/List.java: Likewise. * java/util/ListResourceBundle.java: Likewise. * java/util/Map.java: Likewise. * java/util/Observable.java: Likewise. * java/util/Properties.java: Likewise. * java/util/PropertyPermission.java: Likewise. * java/util/PropertyPermissionCollection.java: Likewise. * java/util/PropertyResourceBundle.java: Likewise. * java/util/Random.java: Likewise. * java/util/SimpleTimeZone.java: Likewise. * java/util/StringTokenizer.java: Likewise. * java/util/TimerTask.java: Likewise. * java/util/TreeMap.java: Likewise. * java/util/WeakHashMap.java: Likewise. * java/util/jar/Attributes.java: Likewise. * java/util/jar/JarException.java: Likewise. * java/util/jar/Manifest.java: Likewise. From-SVN: r54743 --- libjava/java/util/WeakHashMap.java | 70 +++++++++++++++++++++----------------- 1 file changed, 38 insertions(+), 32 deletions(-) (limited to 'libjava/java/util/WeakHashMap.java') diff --git a/libjava/java/util/WeakHashMap.java b/libjava/java/util/WeakHashMap.java index 8c55ae0..3431ac9 100644 --- a/libjava/java/util/WeakHashMap.java +++ b/libjava/java/util/WeakHashMap.java @@ -1,4 +1,4 @@ -/* java.util.WeakHashMap -- a hashtable that keeps only weak references +/* WeakHashMap -- a hashtable that keeps only weak references to its keys, allowing the virtual machine to reclaim them Copyright (C) 1999, 2000, 2001, 2002 Free Software Foundation, Inc. @@ -43,41 +43,41 @@ import java.lang.ref.WeakReference; import java.lang.ref.ReferenceQueue; /** - * A weak hash map has only weak references to the key. This means - * that it allows the key to be garbage collected if they are not used - * otherwise. If this happens, the weak hash map will eventually - * remove the whole entry from this map.
+ * A weak hash map has only weak references to the key. This means that it + * allows the key to be garbage collected if it is not used otherwise. If + * this happens, the entry will eventually disappear from the map, + * asynchronously. * - * A weak hash map makes most sense, if the keys doesn't override the - * equals-method: If there is no other reference to the + *

A weak hash map makes most sense when the keys doesn't override the + * equals method: If there is no other reference to the * key nobody can ever look up the key in this table and so the entry - * can be removed. This table also works, if the equals - * method is overloaded, e.g. with Strings as keys, but you should be - * prepared that some entries disappear spontaneously.
+ * can be removed. This table also works when the equals + * method is overloaded, such as String keys, but you should be prepared + * to deal with some entries disappearing spontaneously. * - * You should also be prepared that this hash map behaves very - * strange: The size of this map may spontaneously shrink (even if you - * use a synchronized map and synchronize it); it behaves as if - * another thread removes entries from this table without - * synchronizations. The entry set returned by entrySet + *

Other strange behaviors to be aware of: The size of this map may + * spontaneously shrink (even if you use a synchronized map and synchronize + * it); it behaves as if another thread removes entries from this table + * without synchronization. The entry set returned by entrySet * has similar phenomenons: The size may spontaneously shrink, or an - * entry, that was in the set before, suddenly disappears.
+ * entry, that was in the set before, suddenly disappears. * - * A weak hash map is not meant for caches; use a normal map, with - * soft references as values instead, or try {@link LinkedHashMap}.
+ *

A weak hash map is not meant for caches; use a normal map, with + * soft references as values instead, or try {@link LinkedHashMap}. * - * The weak hash map supports null values and null keys. The null key - * is never deleted from the map (except explictly of course). - * The performance of the methods are similar to that of a hash map.
+ *

The weak hash map supports null values and null keys. The null key + * is never deleted from the map (except explictly of course). The + * performance of the methods are similar to that of a hash map. * - * The value objects are strongly referenced by this table. So if a + *

The value objects are strongly referenced by this table. So if a * value object maintains a strong reference to the key (either direct * or indirect) the key will never be removed from this map. According * to Sun, this problem may be fixed in a future release. It is not * possible to do it with the jdk 1.2 reference model, though. * * @author Jochen Hoenicke - * @author Eric Blake + * @author Eric Blake (ebb9@email.byu.edu) + * * @see HashMap * @see WeakReference * @see LinkedHashMap @@ -86,6 +86,9 @@ import java.lang.ref.ReferenceQueue; */ public class WeakHashMap extends AbstractMap implements Map { + // WARNING: WeakHashMap is a CORE class in the bootstrap cycle. See the + // comments in vm/reference/java/lang/Runtime for implications of this fact. + /** * The default capacity for an instance of HashMap. * Sun's documentation mildly suggests that this (11) is the correct @@ -148,7 +151,7 @@ public class WeakHashMap extends AbstractMap implements Map /** * The rounded product of the capacity (i.e. number of buckets) and * the load factor. When the number of elements exceeds the - * threshold, the HashMap calls 

rehash()
. + * threshold, the HashMap calls rehash(). */ private int threshold; @@ -364,11 +367,11 @@ public class WeakHashMap extends AbstractMap implements Map /** * The slot of this entry. This should be - * 
-     *  Math.abs(key.hashCode() % buckets.length)
-     *
+ * Math.abs(key.hashCode() % buckets.length). + * * But since the key may be silently removed we have to remember * the slot number. + * * If this bucket was removed the slot is -1. This marker will * prevent the bucket from being removed twice. */ @@ -503,9 +506,10 @@ public class WeakHashMap extends AbstractMap implements Map private final WeakEntrySet theEntrySet; /** - * The hash buckets. These are linked lists. + * The hash buckets. These are linked lists. Package visible for use in + * nested classes. */ - private WeakBucket[] buckets; + WeakBucket[] buckets; /** * Creates a new weak hash map with default load factor and default @@ -676,10 +680,12 @@ public class WeakHashMap extends AbstractMap implements Map /** * Removes a bucket from this hash map, if it wasn't removed before - * (e.g. one time through rehashing and one time through reference queue) + * (e.g. one time through rehashing and one time through reference queue). + * Package visible for use in nested classes. + * * @param bucket the bucket to remove. */ - private void internalRemove(WeakBucket bucket) + void internalRemove(WeakBucket bucket) { int slot = bucket.slot; if (slot == -1) @@ -870,4 +876,4 @@ public class WeakHashMap extends AbstractMap implements Map cleanQueue(); return super.values(); } -} +} // class WeakHashMap -- cgit v1.1