rt/emul/compact/src/main/java/java/lang/invoke/Stable.java
author Jaroslav Tulach <jaroslav.tulach@apidesign.org>
Sat, 09 Aug 2014 11:11:13 +0200
branchjdk8-b132
changeset 1646 c880a8a8803b
permissions -rw-r--r--
Batch of classes necessary to implement invoke dynamic interfaces. Taken from JDK8 build 132
     1 /*
     2  * Copyright (c) 2012, 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.invoke;
    27 
    28 import java.lang.annotation.*;
    29 
    30 /**
    31  * A field may be annotated as stable if all of its component variables
    32  * changes value at most once.
    33  * A field's value counts as its component value.
    34  * If the field is typed as an array, then all the non-null components
    35  * of the array, of depth up to the rank of the field's array type,
    36  * also count as component values.
    37  * By extension, any variable (either array or field) which has annotated
    38  * as stable is called a stable variable, and its non-null or non-zero
    39  * value is called a stable value.
    40  * <p>
    41  * Since all fields begin with a default value of null for references
    42  * (resp., zero for primitives), it follows that this annotation indicates
    43  * that the first non-null (resp., non-zero) value stored in the field
    44  * will never be changed.
    45  * <p>
    46  * If the field is not of an array type, there are no array elements,
    47  * then the value indicated as stable is simply the value of the field.
    48  * If the dynamic type of the field value is an array but the static type
    49  * is not, the components of the array are <em>not</em> regarded as stable.
    50  * <p>
    51  * If the field is an array type, then both the field value and
    52  * all the components of the field value (if the field value is non-null)
    53  * are indicated to be stable.
    54  * If the field type is an array type with rank {@code N &gt; 1},
    55  * then each component of the field value (if the field value is non-null),
    56  * is regarded as a stable array of rank {@code N-1}.
    57  * <p>
    58  * Fields which are declared {@code final} may also be annotated as stable.
    59  * Since final fields already behave as stable values, such an annotation
    60  * indicates no additional information, unless the type of the field is
    61  * an array type.
    62  * <p>
    63  * It is (currently) undefined what happens if a field annotated as stable
    64  * is given a third value.  In practice, if the JVM relies on this annotation
    65  * to promote a field reference to a constant, it may be that the Java memory
    66  * model would appear to be broken, if such a constant (the second value of the field)
    67  * is used as the value of the field even after the field value has changed.
    68  */
    69 /* package-private */
    70 @Target(ElementType.FIELD)
    71 @Retention(RetentionPolicy.RUNTIME)
    72 @interface Stable {
    73 }