@SuppressWarnings注解的用法

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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:

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  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:

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@SuppressWarnings("unchecked")
public void addItems(String item){
  @SuppressWarnings("rawtypes")
   List items = new ArrayList();
   items.add(item);
}
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  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。

 而家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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