概述
作用:用于抑制编译器产生警告信息,即IDEA里面的黄色代码块。
抑制单类型的警告:
@SuppressWarnings("unchecked")
public void add(String item) {
List items = new ArrayList();
items.add(item);
}
抑制多类型的警告:
@SuppressWarnings(value={"unchecked", "rawtypes"})
public void add(String item) {
List items = new ArrayList();
items.add(item);
}
抑制所有类型的警告:
@SuppressWarnings("all")
通过 @SuppressWarnings 的源码可知,其注解目标为类、字段、函数、函数入参、构造函数和函数的局部变量。建议注解应声明在最接近警告发生的位置。
抑制警告的关键字
关键字 |
用途 |
all |
to suppress all warnings |
boxing |
to suppress warnings relative to boxing/unboxing operations |
UnstableApiUsage |
to suppress warnings x-is-marked-unstable |
cast |
to suppress warnings relative to cast operations |
dep-ann |
to suppress warnings relative to deprecated annotation |
deprecation |
to suppress warnings relative to deprecation |
fallthrough |
to suppress warnings relative to missing breaks in switch statements |
finally |
to suppress warnings relative to finally block that don’t return |
hiding |
to suppress warnings relative to locals that hide variable |
incomplete-switch |
to suppress warnings relative to missing entries in a switch statement (enum case) |
nls |
to suppress warnings relative to non-nls string literals |
null |
to suppress warnings relative to null analysis |
rawtypes |
to suppress warnings relative to un-specific types when using generics on class params |
restriction |
to suppress warnings relative to usage of discouraged or forbidden references |
serial |
to suppress warnings relative to missing serialVersionUID field for a serializable class |
static-access |
to suppress warnings relative to incorrect static access |
synthetic-access |
to suppress warnings relative to unoptimized access from inner classes |
unchecked |
to suppress warnings relative to unchecked operations |
unqualified-field-access |
to suppress warnings relative to field access unqualified |
unused |
to suppress warnings relative to unused code |
Java Lint选项
- lint的含义
用于在编译程序的过程中,进行更细节的额外检查。 - javac 的标准选项和非标准选项
标准选项:是指当前版本和未来版本中都支持的选项,如 -cp 和 -d 等。
非标准选项:是指当前版本支持,但未来不一定支持的选项。通过 javac -X 查看当前版本支持的非标准选项。 - 查看警告信息
默认情况下执行 javac 仅仅显示警告的扼要信息,也不过阻止编译过程。若想查看警告的详细信息,则需要执行javac -Xlint:keyword
来编译源码。
总结
虽然,Java语言提供此注解,但是强烈建议永远不要使用:
- 对于泛型,一定要指定泛型类型。而不是使用raw type,即Object类型,
List a = new ArrayList();
,再加上SuppressWarnings注解。因为假如后面如果想要从List里面取元素出来,可能出现错误的将String元素转型为Integer,造成classCastException,或者NumberFormatException; - 对于无用的方法或者类,立马删除,而不是加
@SuppressWarnings("unused")
,脏代码会破坏阅读体验;
参考
suppress-warning-x-is-marked-unstable