1 /*
   2  * Copyright (c) 2005, 2019, 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 javax.lang.model.element;
  27 
  28 import java.util.List;
  29 import javax.lang.model.type.*;
  30 import javax.lang.model.util.*;
  31 
  32 /**
  33  * Represents a class or interface program element.  Provides access
  34  * to information about the type and its members.  Note that an enum
  35  * type and a record type are kinds of class esand an annotation type is a kind of
  36  * interface.
  37  *
  38  * <p> While a {@code TypeElement} represents a class or interface
  39  * <i>element</i>, a {@link DeclaredType} represents a class
  40  * or interface <i>type</i>, the latter being a use
  41  * (or <i>invocation</i>) of the former.
  42  * The distinction is most apparent with generic types,
  43  * for which a single element can define a whole
  44  * family of types.  For example, the element
  45  * {@code java.util.Set} corresponds to the parameterized types
  46  * {@code java.util.Set<String>} and {@code java.util.Set<Number>}
  47  * (and many others), and to the raw type {@code java.util.Set}.
  48  *
  49  * <p> Each method of this interface that returns a list of elements
  50  * will return them in the order that is natural for the underlying
  51  * source of program information.  For example, if the underlying
  52  * source of information is Java source code, then the elements will be
  53  * returned in source code order.
  54  *
  55  * @author Joseph D. Darcy
  56  * @author Scott Seligman
  57  * @author Peter von der Ah&eacute;
  58  * @see DeclaredType
  59  * @since 1.6
  60  */
  61 public interface TypeElement extends Element, Parameterizable, QualifiedNameable {
  62     /**
  63      * Returns the type defined by this type element, returning the
  64      * <i>prototypical</i> type for an element representing a generic type.
  65      *
  66      * <p>A generic element defines a family of types, not just one.
  67      * If this is a generic element, a prototypical type is
  68      * returned which has the element's invocation on the
  69      * type variables corresponding to its own formal type parameters.
  70      * For example,
  71      * for the generic class element {@code C<N extends Number>},
  72      * the parameterized type {@code C<N>} is returned.
  73      * The {@link Types} utility interface has more general methods
  74      * for obtaining the full range of types defined by an element.
  75      *
  76      * @return the type defined by this type element
  77      *
  78      * @see Types#asMemberOf(DeclaredType, Element)
  79      * @see Types#getDeclaredType(TypeElement, TypeMirror...)
  80      */
  81     @Override
  82     TypeMirror asType();
  83 
  84     /**
  85      * Returns the fields, methods, constructors, state components, and member types
  86      * that are directly declared in this class or interface.
  87      *
  88      * This includes any {@linkplain Elements.Origin#MANDATED
  89      * mandated} elements such as the (implicit) default constructor
  90      * and the implicit {@code values} and {@code valueOf} methods of
  91      * an enum type.
  92      *
  93      * @apiNote As a particular instance of the {@linkplain
  94      * javax.lang.model.element general accuracy requirements} and the
  95      * ordering behavior required of this interface, the list of
  96      * enclosed elements will be returned in the natural order for the
  97      * originating source of information about the type.  For example,
  98      * if the information about the type is originating from a source
  99      * file, the elements will be returned in source code order.
 100      * (However, in that case the the ordering of {@linkplain
 101      * Elements.Origin#MANDATED implicitly declared} elements, such as
 102      * default constructors, is not specified.)
 103      *
 104      * @return the enclosed elements in proper order, or an empty list if none
 105      *
 106      * @jls 8.8.9 Default Constructor
 107      * @jls 8.9.3 Enum Members
 108      */
 109     @Override
 110     List<? extends Element> getEnclosedElements();
 111 
 112     /**
 113      * Returns the <i>nesting kind</i> of this type element.
 114      *
 115      * @return the nesting kind of this type element
 116      */
 117     NestingKind getNestingKind();
 118 
 119     /**
 120      * Returns the fully qualified name of this type element.
 121      * More precisely, it returns the <i>canonical</i> name.
 122      * For local and anonymous classes, which do not have canonical names,
 123      * an empty name is returned.
 124      *
 125      * <p>The name of a generic type does not include any reference
 126      * to its formal type parameters.
 127      * For example, the fully qualified name of the interface
 128      * {@code java.util.Set<E>} is "{@code java.util.Set}".
 129      * Nested types use "{@code .}" as a separator, as in
 130      * "{@code java.util.Map.Entry}".
 131      *
 132      * @return the fully qualified name of this class or interface, or
 133      * an empty name if none
 134      *
 135      * @see Elements#getBinaryName
 136      * @jls 6.7 Fully Qualified Names and Canonical Names
 137      */
 138     Name getQualifiedName();
 139 
 140     /**
 141      * Returns the simple name of this type element.
 142      *
 143      * For an anonymous class, an empty name is returned.
 144      *
 145      * @return the simple name of this class or interface,
 146      * an empty name for an anonymous class
 147      *
 148      */
 149     @Override
 150     Name getSimpleName();
 151 
 152     /**
 153      * Returns the direct superclass of this type element.
 154      * If this type element represents an interface or the class
 155      * {@code java.lang.Object}, then a {@link NoType}
 156      * with kind {@link TypeKind#NONE NONE} is returned.
 157      *
 158      * @return the direct superclass, or a {@code NoType} if there is none
 159      */
 160     TypeMirror getSuperclass();
 161 
 162     /**
 163      * Returns the interface types directly implemented by this class
 164      * or extended by this interface.
 165      *
 166      * @return the interface types directly implemented by this class
 167      * or extended by this interface, or an empty list if there are none
 168      */
 169     List<? extends TypeMirror> getInterfaces();
 170 
 171     /**
 172      * Returns the formal type parameters of this type element
 173      * in declaration order.
 174      *
 175      * @return the formal type parameters, or an empty list
 176      * if there are none
 177      */
 178     List<? extends TypeParameterElement> getTypeParameters();
 179 
 180     /**
 181      * Returns the state components of this type element in
 182      * declaration order.
 183      *
 184      * @implSpec The default implementations of this method returns an
 185      * empty and unmodifiable list.
 186      *
 187      * @return the state components, or an empty list if there are
 188      * none
 189      *
 190      * @since amber
 191      */
 192     default List<? extends VariableElement> getStateComponents() {
 193         return List.of();
 194     }
 195 
 196     /**
 197      * Returns the permitted subtypes of this type element in
 198      * declaration order.
 199      *
 200      * @implSpec The default implementations of this method returns an
 201      * empty and unmodifiable list.
 202      *
 203      * @return the permitted subtypes, or an empty list
 204      * if there are none
 205      *
 206      * @since amber
 207      */
 208     default List<? extends TypeMirror> getPermittedSubtypes() {
 209         return List.of();
 210     }
 211 
 212     /**
 213      * Returns the package of a top-level type and returns the
 214      * immediately lexically enclosing element for a {@linkplain
 215      * NestingKind#isNested nested} type.
 216      *
 217      * @return the package of a top-level type, the immediately
 218      * lexically enclosing element for a nested type
 219      */
 220     @Override
 221     Element getEnclosingElement();
 222 }