src.java.lang.invoke.Stable Maven / Gradle / Ivy
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/*
* Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package java.lang.invoke;
import java.lang.annotation.*;
/**
* A field may be annotated as stable if all of its component variables
* changes value at most once.
* A field's value counts as its component value.
* If the field is typed as an array, then all the non-null components
* of the array, of depth up to the rank of the field's array type,
* also count as component values.
* By extension, any variable (either array or field) which has annotated
* as stable is called a stable variable, and its non-null or non-zero
* value is called a stable value.
*
* Since all fields begin with a default value of null for references
* (resp., zero for primitives), it follows that this annotation indicates
* that the first non-null (resp., non-zero) value stored in the field
* will never be changed.
*
* If the field is not of an array type, there are no array elements,
* then the value indicated as stable is simply the value of the field.
* If the dynamic type of the field value is an array but the static type
* is not, the components of the array are not regarded as stable.
*
* If the field is an array type, then both the field value and
* all the components of the field value (if the field value is non-null)
* are indicated to be stable.
* If the field type is an array type with rank {@code N > 1},
* then each component of the field value (if the field value is non-null),
* is regarded as a stable array of rank {@code N-1}.
*
* Fields which are declared {@code final} may also be annotated as stable.
* Since final fields already behave as stable values, such an annotation
* indicates no additional information, unless the type of the field is
* an array type.
*
* It is (currently) undefined what happens if a field annotated as stable
* is given a third value. In practice, if the JVM relies on this annotation
* to promote a field reference to a constant, it may be that the Java memory
* model would appear to be broken, if such a constant (the second value of the field)
* is used as the value of the field even after the field value has changed.
*/
/* package-private */
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@interface Stable {
}