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author | upstream source tree <ports@midipix.org> | 2015-03-15 20:14:05 -0400 |
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committer | upstream source tree <ports@midipix.org> | 2015-03-15 20:14:05 -0400 |
commit | 554fd8c5195424bdbcabf5de30fdc183aba391bd (patch) | |
tree | 976dc5ab7fddf506dadce60ae936f43f58787092 /libjava/classpath/vm/reference/java/lang/VMString.java | |
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Diffstat (limited to 'libjava/classpath/vm/reference/java/lang/VMString.java')
-rw-r--r-- | libjava/classpath/vm/reference/java/lang/VMString.java | 91 |
1 files changed, 91 insertions, 0 deletions
diff --git a/libjava/classpath/vm/reference/java/lang/VMString.java b/libjava/classpath/vm/reference/java/lang/VMString.java new file mode 100644 index 000000000..e1fbf8390 --- /dev/null +++ b/libjava/classpath/vm/reference/java/lang/VMString.java @@ -0,0 +1,91 @@ +/* VMString.java -- VM Specific String methods + Copyright (C) 2003 Free Software Foundation + +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 java.lang; + +import java.lang.ref.WeakReference; +import java.util.WeakHashMap; + +/* + * This class is a reference version, mainly for compiling a class library + * jar. It is likely that VM implementers replace this with their own + * version that can communicate effectively with the VM. + */ + +/** + * Code relocated from java.lang.String by + * @author Dave Grove <groved@us.ibm.com> + */ +final class VMString +{ + + /** + * Holds the references for each intern()'d String. If all references to + * the string disappear, and the VM properly supports weak references, + * the String will be GC'd. + */ + private static final WeakHashMap internTable = new WeakHashMap(); + + /** + * Fetches this String from the intern hashtable. If two Strings are + * considered equal, by the equals() method, then intern() will return the + * same String instance. ie. if (s1.equals(s2)) then + * (s1.intern() == s2.intern()). All string literals and string-valued + * constant expressions are already interned. + * + * @param str the String to intern + * @return the interned String + */ + static String intern(String str) + { + synchronized (internTable) + { + WeakReference ref = (WeakReference) internTable.get(str); + if (ref != null) + { + String s = (String) ref.get(); + // If s is null, then no strong references exist to the String; + // the weak hash map will soon delete the key. + if (s != null) + return s; + } + internTable.put(str, new WeakReference(str)); + } + return str; + } + +} // class VMString |