1 /*
   2  * Copyright (c) 2005, 2020, 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 classes and 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, record components,
  86      * and member types that are directly declared in this class or
  87      * interface.
  88      *
  89      * This includes any {@linkplain Elements.Origin#MANDATED
  90      * mandated} elements such as the (implicit) default constructor
  91      * and the implicit {@code values} and {@code valueOf} methods of
  92      * an enum type.
  93      *
  94      * @apiNote As a particular instance of the {@linkplain
  95      * javax.lang.model.element general accuracy requirements} and the
  96      * ordering behavior required of this interface, the list of
  97      * enclosed elements will be returned in the natural order for the
  98      * originating source of information about the type.  For example,
  99      * if the information about the type is originating from a source
 100      * file, the elements will be returned in source code order.
 101      * (However, in that case the the ordering of {@linkplain
 102      * Elements.Origin#MANDATED implicitly declared} elements, such as
 103      * default constructors, is not specified.)
 104      *
 105      * @return the enclosed elements in proper order, or an empty list if none
 106      *
 107      * @jls 8.8.9 Default Constructor
 108      * @jls 8.9.3 Enum Members
 109      */
 110     @Override
 111     List<? extends Element> getEnclosedElements();
 112 
 113     /**
 114      * Returns the <i>nesting kind</i> of this type element.
 115      *
 116      * @return the nesting kind of this type element
 117      */
 118     NestingKind getNestingKind();
 119 
 120     /**
 121      * Returns the fully qualified name of this type element.
 122      * More precisely, it returns the <i>canonical</i> name.
 123      * For local and anonymous classes, which do not have canonical names,
 124      * an empty name is returned.
 125      *
 126      * <p>The name of a generic type does not include any reference
 127      * to its formal type parameters.
 128      * For example, the fully qualified name of the interface
 129      * {@code java.util.Set<E>} is "{@code java.util.Set}".
 130      * Nested types use "{@code .}" as a separator, as in
 131      * "{@code java.util.Map.Entry}".
 132      *
 133      * @return the fully qualified name of this class or interface, or
 134      * an empty name if none
 135      *
 136      * @see Elements#getBinaryName
 137      * @jls 6.7 Fully Qualified Names and Canonical Names
 138      */
 139     Name getQualifiedName();
 140 
 141     /**
 142      * Returns the simple name of this type element.
 143      *
 144      * For an anonymous class, an empty name is returned.
 145      *
 146      * @return the simple name of this class or interface,
 147      * an empty name for an anonymous class
 148      *
 149      */
 150     @Override
 151     Name getSimpleName();
 152 
 153     /**
 154      * Returns the direct superclass of this type element.
 155      * If this type element represents an interface or the class
 156      * {@code java.lang.Object}, then a {@link NoType}
 157      * with kind {@link TypeKind#NONE NONE} is returned.
 158      *
 159      * @return the direct superclass, or a {@code NoType} if there is none
 160      */
 161     TypeMirror getSuperclass();
 162 
 163     /**
 164      * Returns the interface types directly implemented by this class
 165      * or extended by this interface.
 166      *
 167      * @return the interface types directly implemented by this class
 168      * or extended by this interface, or an empty list if there are none
 169      */
 170     List<? extends TypeMirror> getInterfaces();
 171 
 172     /**
 173      * Returns the formal type parameters of this type element
 174      * in declaration order.
 175      *
 176      * @return the formal type parameters, or an empty list
 177      * if there are none
 178      */
 179     List<? extends TypeParameterElement> getTypeParameters();
 180 
 181     /**
 182      * {@preview Associated with records, a preview feature of the Java language.
 183      *
 184      *           This method is associated with <i>records</i>, a preview
 185      *           feature of the Java language. Preview features
 186      *           may be removed in a future release, or upgraded to permanent
 187      *           features of the Java language.}
 188      *
 189      * Returns the record components of this type element in
 190      * declaration order.
 191      *
 192      * @implSpec The default implementations of this method returns an
 193      * empty and unmodifiable list.
 194      *
 195      * @return the record components, or an empty list if there are
 196      * none
 197      *
 198      * @since 14
 199      */
 200     @jdk.internal.PreviewFeature(feature=jdk.internal.PreviewFeature.Feature.RECORDS,
 201                                  essentialAPI=false)
 202     @SuppressWarnings("preview")
 203     default List<? extends RecordComponentElement> getRecordComponents() {
 204         return List.of();
 205     }
 206 
 207     /**
 208      * {@preview Associated with sealed classes, a preview feature of the Java language.
 209      *
 210      *           This method is associated with <i>sealed classes</i>, a preview
 211      *           feature of the Java language. Preview features
 212      *           may be removed in a future release, or upgraded to permanent
 213      *           features of the Java language.}
 214      * Returns the permitted classes of this type element in
 215      * declaration order.
 216      *
 217      * @implSpec The default implementations of this method returns an
 218      * empty and unmodifiable list.
 219      *
 220      * @return the permitted classes, or an empty list if there are none
 221      *
 222      * @since 15
 223      */
 224     @jdk.internal.PreviewFeature(feature=jdk.internal.PreviewFeature.Feature.SEALED_CLASSES,
 225                                  essentialAPI=false)
 226     default List<? extends TypeMirror> getPermittedSubclasses() {
 227         return List.of();
 228     }
 229 
 230     /**
 231      * Returns the package of a top-level type and returns the
 232      * immediately lexically enclosing element for a {@linkplain
 233      * NestingKind#isNested nested} type.
 234      *
 235      * @return the package of a top-level type, the immediately
 236      * lexically enclosing element for a nested type
 237      */
 238     @Override
 239     Element getEnclosingElement();
 240 }