1 /*
   2  * Copyright (c) 2003, 2011, 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.GenericDeclaration;
  29 import java.lang.reflect.TypeVariable;
  30 
  31 
  32 /**
  33  * Abstract superclass for lazy scope objects, used when building
  34  * factories for generic information repositories.
  35  * The type parameter <tt>D</tt> represents the type of reflective
  36  * object whose scope this class is representing.
  37  * <p> To subclass this, all one needs to do is implement
  38  * <tt>computeEnclosingScope</tt> and the subclass' constructor.
  39  */
  40 public abstract class AbstractScope<D extends GenericDeclaration>
  41     implements Scope {
  42 
  43     private final D recvr; // the declaration whose scope this instance represents
  44 
  45     /** The enclosing scope of this scope.  Lazily initialized. */
  46     private volatile Scope enclosingScope;
  47 
  48     /**
  49      * Constructor. Takes a reflective object whose scope the newly
  50      * constructed instance will represent.
  51      * @param decl - A generic declaration whose scope the newly
  52      * constructed instance will represent
  53      */
  54     protected AbstractScope(D decl){ recvr = decl;}
  55 
  56     /**
  57      * Accessor for the receiver - the object whose scope this <tt>Scope</tt>
  58      * object represents.
  59      * @return The object whose scope this <tt>Scope</tt> object represents
  60      */
  61     protected D getRecvr() {return recvr;}
  62 
  63     /** This method must be implemented by any concrete subclass.
  64      * It must return the enclosing scope of this scope. If this scope
  65      * is a top-level scope, an instance of DummyScope must be returned.
  66      * @return The enclosing scope of this scope
  67      */
  68     protected abstract Scope computeEnclosingScope();
  69 
  70     /**
  71      * Accessor for the enclosing scope, which is computed lazily and cached.
  72      * @return the enclosing scope
  73      */
  74     protected Scope getEnclosingScope() {
  75         Scope value = enclosingScope;
  76         if (value == null) {
  77             value = computeEnclosingScope();
  78             enclosingScope = value;
  79         }
  80         return value;
  81     }
  82 
  83     /**
  84      * Lookup a type variable in the scope, using its name. Returns null if
  85      * no type variable with this name is declared in this scope or any of its
  86      * surrounding scopes.
  87      * @param name - the name of the type variable being looked up
  88      * @return the requested type variable, if found
  89      */
  90     public TypeVariable<?> lookup(String name) {
  91         TypeVariable<?>[] tas = getRecvr().getTypeParameters();
  92         for (TypeVariable<?> tv : tas) {
  93             if (tv.getName().equals(name)) {return tv;}
  94         }
  95         return getEnclosingScope().lookup(name);
  96     }
  97 }