Initial revision

From-SVN: r102074
2005-07-16 00:30:23 +00:00
parent 6f4434b39b
commit f911ba985a
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+/* ObjectIdentityWrapper.java -- Wrapper class used to override equals()
+    and hashCode() to be as discriminating as possible
+   Copyright (C) 1998 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 gnu.java.io;
+
+/**
+   This class is a thin wrapper around <code>Object</code> that makes
+   the methods <code>hashCode()</code> and <code>equals(Object)</code>
+   as discriminating as possible.
+*/
+public class ObjectIdentityWrapper
+{
+
+  /**
+     Constructs a <code>ObjectIdentityWrapper</code> that is wrapped
+     around o.
+  */
+  public ObjectIdentityWrapper( Object o )
+  {
+    object = o;
+  }
+
+  /**
+     Uses <code>System.identityHashCode(Object)</code> to compute a
+     hash code for the object wrapped by this
+     <code>ObjectIdentityWrapper</code>.
+
+     @see java.lang.System#identityHashCode(java.lang.Object)
+     @see java.util.Hashtable
+     @see java.lang.Object#hashCode()
+  */
+  public int hashCode()
+  {
+    return System.identityHashCode( object );
+  }
+
+  /**
+     Uses the <code>==</code> operator to test for equality between
+     the object wrapped by this <code>ObjectIdentityWrapper</code> and
+     the object wrapped by the <code>ObjectIdentityWrapper</code> o.
+     Returns false if o is not a <code>ObjectIdentityWrapper</code>.
+
+     @see java.util.Hashtable
+     @see java.lang.Object#equals()
+  */
+  public boolean equals( Object o )
+  {
+    if( o instanceof ObjectIdentityWrapper )
+      return object == ((ObjectIdentityWrapper)o).object;
+    else
+      return false;
+  }
+
+  public String toString()
+  {
+    return "ObjectIdentityWrapper< " + object + ", " + hashCode() + " >";
+  }
+
+  /**
+     The <code>Object</code> wrapped by this
+     <code>ObjectIdentityWrapper</code>.
+  */
+  public Object object;
+}