1 /* 2 * Copyright (c) 2003, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 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). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 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 44 private DummyScope(){} 45 46 /** 47 * Factory method. Enforces the singleton pattern - only one 48 * instance of this class ever exists. 49 */ 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 */ 60 public TypeVariable<?> lookup(String name) {return null;} 61 }