Mercurial > hg > openjdk > jdk7 > jdk
changeset 4208:85cbf90d88b9
7011326: Add informative example to @SafeVarargs type or language discussion
Reviewed-by: mcimadamore, mduigou
author | darcy |
---|---|
date | Fri, 06 May 2011 17:06:25 -0700 |
parents | 36724da65fef |
children | d93f6b6b986b |
files | src/share/classes/java/lang/SafeVarargs.java |
diffstat | 1 files changed, 20 insertions(+), 8 deletions(-) [+] |
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--- a/src/share/classes/java/lang/SafeVarargs.java Mon May 02 20:17:18 2011 +0100 +++ b/src/share/classes/java/lang/SafeVarargs.java Fri May 06 17:06:25 2011 -0700 @@ -1,5 +1,5 @@ /* - * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved. + * Copyright (c) 2010, 2011, 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 @@ -32,7 +32,7 @@ * constructor does not perform potentially unsafe operations on its * varargs parameter. Applying this annotation to a method or * constructor suppresses unchecked warnings about a - * <i>non-reifiable</i> variable-arity (vararg) type and suppresses + * <i>non-reifiable</i> variable arity (vararg) type and suppresses * unchecked warnings about parameterized array creation at call * sites. * @@ -41,11 +41,10 @@ * additional usage restrictions on this annotation type; it is a * compile-time error if a method or constructor declaration is * annotated with a {@code @SafeVarargs} annotation, and either: - * <ul> - * <li> the declaration is a fixed-arity method or constructor + * <li> the declaration is a fixed arity method or constructor * - * <li> the declaration is a variable-arity method that is neither + * <li> the declaration is a variable arity method that is neither * {@code static} nor {@code final}. * * </ul> @@ -55,15 +54,28 @@ * * <ul> * - * <li> The variable-arity parameter has a reifiable element type, + * <li> The variable arity parameter has a reifiable element type, * which includes primitive types, {@code Object}, and {@code String}. * (The unchecked warnings this annotation type suppresses already do * not occur for a reifiable element type.) * * <li> The body of the method or constructor declaration performs * potentially unsafe operations, such as an assignment to an element - * of the variable-arity parameter's array that generates an unchecked - * warning. + * of the variable arity parameter's array that generates an unchecked + * warning. Some unsafe operations do not trigger an unchecked + * warning. For example, the aliasing in + * + * <blockquote><pre> + * @SafeVarargs // Not actually safe! + * static void m(List<String>... stringLists) { + * Object[] array = stringLists; + * List<Integer> tmpList = Arrays.asList(42); + * array[0] = tmpList; // Semantically invalid, but compiles without warnings + * String s = stringLists[0].get(0); // Oh no, ClassCastException at runtime! + * } + * </pre></blockquote> + * + * leads to a {@code ClassCastException} at runtime. * * <p>Future versions of the platform may mandate compiler errors for * such unsafe operations.