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  * Indicates the contexts in which an annotation type is applicable. The
  30  * declaration contexts and type contexts in which an annotation type may be
  31  * applicable are specified in JLS 9.6.4.1, and denoted in source code by enum
  32  * constants of {@link ElementType java.lang.annotation.ElementType}.
  33  *
  34  * <p>If an {@code @Target} meta-annotation is not present on an annotation type
  35  * {@code T} , then an annotation of type {@code T} may be written as a
  36  * modifier for any declaration except a type parameter declaration.
  37  *
  38  * <p>If an {@code @Target} meta-annotation is present, the compiler will enforce
  39  * the usage restrictions indicated by {@code ElementType}
  40  * enum constants, in line with JLS 9.7.4.
  41  *
  42  * <p>For example, this {@code @Target} meta-annotation indicates that the
  43  * declared type is itself a meta-annotation type.  It can only be used on
  44  * annotation type declarations:
  45  * <pre>
  46  *    @Target(ElementType.ANNOTATION_TYPE)
  47  *    public @interface MetaAnnotationType {
  48  *        ...
  49  *    }
  50  * </pre>
  51  *
  52  * <p>This {@code @Target} meta-annotation indicates that the declared type is
  53  * intended solely for use as a member type in complex annotation type
  54  * declarations.  It cannot be used to annotate anything directly:
  55  * <pre>
  56  *    @Target({})
  57  *    public @interface MemberType {
  58  *        ...
  59  *    }
  60  * </pre>
  61  *
  62  * <p>It is a compile-time error for a single {@code ElementType} constant to
  63  * appear more than once in an {@code @Target} annotation.  For example, the
  64  * following {@code @Target} meta-annotation is illegal:
  65  * <pre>
  66  *    @Target({ElementType.FIELD, ElementType.METHOD, ElementType.FIELD})
  67  *    public @interface Bogus {
  68  *        ...
  69  *    }
  70  * </pre>
  71  *
  72  * @since 1.5
  73  * @jls 9.6.4.1 @Target
  74  * @jls 9.7.4 Where Annotations May Appear
  75  */
  76 @Documented
  77 @Retention(RetentionPolicy.RUNTIME)
  78 @Target(ElementType.ANNOTATION_TYPE)
  79 public @interface Target {
  80     /**
  81      * Returns an array of the kinds of elements an annotation type
  82      * can be applied to.
  83      * @return an array of the kinds of elements an annotation type
  84      * can be applied to
  85      */
  86     ElementType[] value();
  87 }