1 /*
   2  * Copyright (c) 2003, 2013, 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 java.lang.annotation;
  27 
  28 /**
  29  * The constants of this enumerated type provide a simple classification of the
  30  * syntactic locations where annotations may appear in a Java program. These
  31  * constants are used in {@link Target java.lang.annotation.Target}
  32  * meta-annotations to specify where it is legal to write annotations of a
  33  * given type.
  34  *
  35  * <p>The syntactic locations where annotations may appear are split into
  36  * <em>declaration contexts</em> , where annotations apply to declarations, and
  37  * <em>type contexts</em> , where annotations apply to types used in
  38  * declarations and expressions.
  39  *
  40  * <p>The constants {@link #ANNOTATION_TYPE} , {@link #CONSTRUCTOR} , {@link
  41  * #FIELD} , {@link #LOCAL_VARIABLE} , {@link #METHOD} , {@link #PACKAGE} ,
  42  * {@link #PARAMETER} , {@link #TYPE} , and {@link #TYPE_PARAMETER} correspond
  43  * to the declaration contexts in JLS 9.6.4.1.
  44  *
  45  * <p>For example, an annotation whose type is meta-annotated with
  46  * {@code @Target(ElementType.FIELD)} may only be written as a modifier for a
  47  * field declaration.
  48  *
  49  * <p>The constant {@link #TYPE_USE} corresponds to the 15 type contexts in JLS
  50  * 4.11, as well as to two declaration contexts: type declarations (including
  51  * annotation type declarations) and type parameter declarations.
  52  *
  53  * <p>For example, an annotation whose type is meta-annotated with
  54  * {@code @Target(ElementType.TYPE_USE)} may be written on the type of a field
  55  * (or within the type of the field, if it is a nested, parameterized, or array
  56  * type), and may also appear as a modifier for, say, a class declaration.
  57  *
  58  * <p>The {@code TYPE_USE} constant includes type declarations and type
  59  * parameter declarations as a convenience for designers of type checkers which
  60  * give semantics to annotation types. For example, if the annotation type
  61  * {@code NonNull} is meta-annotated with
  62  * {@code @Target(ElementType.TYPE_USE)}, then {@code @NonNull}
  63  * {@code class C {...}} could be treated by a type checker as indicating that
  64  * all variables of class {@code C} are non-null, while still allowing
  65  * variables of other classes to be non-null or not non-null based on whether
  66  * {@code @NonNull} appears at the variable's declaration.
  67  *
  68  * @author  Joshua Bloch
  69  * @since 1.5
  70  * @jls 9.6.4.1 @Target
  71  * @jls 4.1 The Kinds of Types and Values
  72  */
  73 public enum ElementType {
  74     /** Class, interface (including annotation type), or enum declaration */
  75     TYPE,
  76 
  77     /** Field declaration (includes enum constants) */
  78     FIELD,
  79 
  80     /** Method declaration */
  81     METHOD,
  82 
  83     /** Formal parameter declaration */
  84     PARAMETER,
  85 
  86     /** Constructor declaration */
  87     CONSTRUCTOR,
  88 
  89     /** Local variable declaration */
  90     LOCAL_VARIABLE,
  91 
  92     /** Annotation type declaration */
  93     ANNOTATION_TYPE,
  94 
  95     /** Package declaration */
  96     PACKAGE,
  97 
  98     /**
  99      * Type parameter declaration
 100      *
 101      * @since 1.8
 102      */
 103     TYPE_PARAMETER,
 104 
 105     /**
 106      * Use of a type
 107      *
 108      * @since 1.8
 109      */
 110     TYPE_USE
 111 }