一、前言
编码时我们总会发现如下变量未被使用的警告提示:
上述代码编译通过且可以运行,但每行前面的“感叹号”就严重阻碍了我们判断该行是否设置的断点了。这时我们可以在方法前添加 @SuppressWarnings(“unused”) 去除这些“感叹号”。
二、 @SuppressWarings注解
作用:用于抑制编译器产生警告信息。
示例1——抑制单类型的警告:
@SuppressWarnings("unchecked") public void addItems(String item){ @SuppressWarnings("rawtypes") List items = new ArrayList(); items.add(item); }
示例2——抑制多类型的警告:
@SuppressWarnings(value={"unchecked", "rawtypes"}) public void addItems(String item){ List items = new ArrayList(); items.add(item); }
示例3——抑制所有类型的警告:
@SuppressWarnings("all") public void addItems(String item){ List items = new ArrayList(); items.add(item); }
三、注解目标
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。
四、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 |
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 | o 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 |
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