java - 为什么@SafeVarargs 不抑制警告？

Question

代码如下:

class Foo<T> {
  private final T[] array;
  @SafeVarargs
  Foo(T... items) {
    this.array = items;
  }
}

我得到:

[WARNING] Varargs method could cause heap pollution 
from non-reifiable varargs parameter items

我的作业有什么问题？如何解决？ @SuppressWarnings 不是一个选项，因为我希望这个构造函数真正“安全”。

$ javac -version
javac 1.8.0_40

Answer 1

来自docs :

Applying this annotation to a method or constructor suppresses unchecked warnings about a non-reifiable variable arity (vararg) type and suppresses unchecked warnings about parameterized array creation at call sites.

第一个语句告诉我们 @SafeVarargs 禁止未经检查的警告:

• 可变参数的非具体化类型
• 调用方法时创建参数化数组

在你的例子中，@SafeVarargs 抑制了对 T... items 的警告。您的警告发生在 this.array = items; 上。

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来自JLS §9.6.4.7 :

The annotation @SafeVarargs has non-local effects because it suppresses unchecked warnings at method invocation expressions in addition to an unchecked warning pertaining to the declaration of the variable arity method itself.

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In contrast, the annotation @SuppressWarnings("unchecked") has local effects because it only suppresses unchecked warnings pertaining to the declaration of a method.