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3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14  * version 2 for more details (a copy is included in the LICENSE file that
15  * accompanied this code).
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24  */
25 
26 package sun.reflect.generics.scope;
27 
28 import java.lang.reflect.TypeVariable;
29 
30 /**
31  * This class is used to provide enclosing scopes for top level classes.
32  * We cannot use <tt>null</tt> to represent such a scope, since the
33  * enclosing scope is computed lazily, and so the field storing it is
34  * null until it has been computed. Therefore, <tt>null</tt> is reserved
35  * to represent an as-yet-uncomputed scope, and cannot be used for any
36  * other kind of scope.
37  */
38 public class DummyScope implements Scope {
39     // Caches the unique instance of this class; instances contain no data
40     // so we can use the singleton pattern
41     private static final DummyScope singleton = new DummyScope();
42 
43     // constructor is private to enforce use of factory method
DummyScope()44     private DummyScope(){}
45 
46     /**
47      * Factory method. Enforces the singleton pattern - only one
48      * instance of this class ever exists.
49      */
make()50     public static DummyScope make() {
51         return singleton;
52     }
53 
54     /**
55      * Lookup a type variable in the scope, using its name. Always returns
56      * <tt>null</tt>.
57      * @param name - the name of the type variable being looked up
58      * @return  null
59      */
lookup(String name)60     public TypeVariable<?> lookup(String name) {return null;}
61 }
62