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