forked from XWxiaowei/JavaCode
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathSafeVarargs.java
More file actions
93 lines (90 loc) · 2.67 KB
/
SafeVarargs.java
File metadata and controls
93 lines (90 loc) · 2.67 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
/*
* Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*/
package java.lang;
import java.lang.annotation.*;
/**
* A programmer assertion that the body of the annotated method or
* 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
* unchecked warnings about parameterized array creation at call
* sites.
*
* <p> In addition to the usage restrictions imposed by its {@link
* Target @Target} meta-annotation, compilers are required to implement
* 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 variable arity method that is neither
* {@code static} nor {@code final}.
*
* </ul>
*
* <p> Compilers are encouraged to issue warnings when this annotation
* type is applied to a method or constructor declaration where:
*
* <ul>
*
* <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. 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.
*
* </ul>
*
* @since 1.7
* @jls 4.7 Reifiable Types
* @jls 8.4.1 Formal Parameters
* @jls 9.6.3.7 @SafeVarargs
*/
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.CONSTRUCTOR, ElementType.METHOD})
public @interface SafeVarargs {}