1 /*
  2  * Copyright (c) 2019, 2024, 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 jdk.internal.javac;
 27 
 28 import java.lang.annotation.*;
 29 
 30 /**
 31  * Indicates the API declaration in question is associated with a
 32  * <em>preview feature</em>. See JEP 12: "Preview Language and VM
 33  * Features" (https://openjdk.org/jeps/12).
 34  *
 35  * Note this internal annotation is handled specially by the javac compiler.
 36  * To work properly with {@code --release older-release}, it requires special
 37  * handling in {@code make/langtools/src/classes/build/tools/symbolgenerator/CreateSymbols.java}
 38  * and {@code src/jdk.compiler/share/classes/com/sun/tools/javac/jvm/ClassReader.java}.
 39  *
 40  * @since 14
 41  */
 42 // Match the meaningful targets of java.lang.Deprecated, omit local
 43 // variables and parameter declarations
 44 @Target({ElementType.METHOD,
 45          ElementType.CONSTRUCTOR,
 46          ElementType.FIELD,
 47          ElementType.PACKAGE,
 48          ElementType.MODULE,
 49          ElementType.TYPE})
 50  // CLASS retention will hopefully be sufficient for the purposes at hand
 51 @Retention(RetentionPolicy.CLASS)
 52 // *Not* @Documented
 53 public @interface PreviewFeature {
 54     /**
 55      * Name of the preview feature the annotated API is associated
 56      * with.
 57      */
 58     public Feature feature();
 59 
 60     public boolean reflective() default false;
 61 
 62     /**
 63      * Enum of preview features in the current release.
 64      * Values should be annotated with the feature's {@code JEP}.
 65      */
 66     public enum Feature {
 67         // not used, but required for interim javac to not warn.
 68         VIRTUAL_THREADS,
 69         FOREIGN,
 70         @JEP(number=459, title="String Templates", status="Second Preview")
 71         STRING_TEMPLATES,
 72         @JEP(number=477, title="Implicitly Declared Classes and Instance Main Methods", status="Third Preview")
 73         IMPLICIT_CLASSES,
 74         @JEP(number=487, title="Scoped Values", status="Fourth Preview")
 75         SCOPED_VALUES,
 76         @JEP(number=480, title="Structured Concurrency", status="Third Preview")
 77         STRUCTURED_CONCURRENCY,
 78         @JEP(number=466, title="ClassFile API", status="Second Preview")
 79         CLASSFILE_API,
 80         @JEP(number=473, title="Stream Gatherers", status="Second Preview")
 81         STREAM_GATHERERS,
 82         @JEP(number=476, title="Module Import Declarations", status="Preview")
 83         MODULE_IMPORTS,
 84         LANGUAGE_MODEL,
 85         /**
 86          * A key for testing.
 87          */
 88         @JEP(number=2_147_483_647, title="Test Feature")
 89         TEST,
 90         ;
 91     }
 92 
 93     /**
 94      * Annotation identifying the JEP associated with a preview feature.
 95      */
 96     @Target(ElementType.FIELD)
 97     @Retention(RetentionPolicy.CLASS)
 98     @interface JEP {
 99         /** JEP number */
100         int number() default 0;
101         /** JEP title in plain text */
102         String title();
103         /** JEP status such as "Preview", "Second Preview", etc */
104         String status() default "Preview";
105     }
106 }