1/*
2 * Copyright (c) 2003, 2017, 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
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24 */
25
26package 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 java.lang.annotation.Target 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}, {@link
42 * #MODULE}, {@link #PARAMETER}, {@link #TYPE}, and {@link #TYPE_PARAMETER}
43 * correspond 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 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 */
73public 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
112    /**
113     * Module declaration.
114     *
115     * @since 9
116     */
117    MODULE
118}
119