1 /*
 2  * Copyright (c) 2023, 2026, 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.vm.annotation;
27 
28 import java.lang.annotation.*;
29 
30 /**
31  * A null-restricted field is a field that does not store {@code null}.
32  * The field must be initialized according to the strict field initialization
33  * rules, and attempts to write {@code null} to the field will throw an exception.
34  * <p>
35  * The HotSpot VM uses this annotation to enable flattened encodings for the
36  * field that would otherwise be impossible.
37  * <p>
38  * The annotation is ignored if the type of the field is not a concrete value type,
39  * or if the type of the field cannot be preloaded during the loading of the class
40  * that declares the field.
41  * <p>
42  * Because these behaviors are not specified by Java SE, this annotation should
43  * only be used by internal JDK classes for experimental purposes and should not
44  * affect user-observable outcomes.
45  */
46 @Target(ElementType.FIELD)
47 @Retention(RetentionPolicy.RUNTIME)
48 public @interface NullRestricted {
49 }