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// 注解的格式
The Format of an AnnotationIn its simplest form, an annotation looks like the following:
@Entity
// @这个标识符告诉编辑器这是一个注解,下面以重写(Override)这个注解为例
The at sign character (@
) indicates to the compiler that what follows is an annotation. In the following example, the annotation's name is Override
:
@Overridevoid mySuperMethod() { ... }
// 注解可以包括属性(elements),这些属性可以是已命名的也可以的未命名的,而且他们可以有自己的属性值(values)
The annotation can include elements, which can be named or unnamed, and there are values for those elements:
@Author( name = "Benjamin Franklin", date = "3/27/2003")class MyClass() { ... }
or
@SuppressWarnings(value = "unchecked")void myMethod() { ... }
// 如果注解只有一个属性,而且属性名为value,那么属性名可以省略,正像下面这个例子展示的那样
If there is just one element named value
, then the name can be omitted, as in:
@SuppressWarnings("unchecked")void myMethod() { ... }
// 如果注解没有属性,那么括号也可以省略,比如前面@Override的例子
If the annotation has no elements, then the parentheses can be omitted, as shown in the previous @Override
example.
// 同一个位置可以使用多个注解
It is also possible to use multiple annotations on the same declaration:
@Author(name = "Jane Doe")@EBookclass MyClass { ... }
// 如果是多个同类注解,这种情况被称作多重注解
If the annotations have the same type, then this is called a repeating annotation:
@Author(name = "Jane Doe")@Author(name = "John Smith")class MyClass { ... }
// Java SE 8 release 开始支持多重注解,想了解更多,请点击链接
Repeating annotations are supported as of the Java SE 8 release. For more information, see .
// 注解可以是Java SE API里面java.lang或者java.lang.annotation这些包里面已经定义的类型,比如前面提到的Override和SuppressWarnings都是
// java预定义注解。也可以是自定义类型,前面例子展示的Author和Ebook都是这一类。
The annotation type can be one of the types that are defined in the java.lang
or java.lang.annotation
packages of the Java SE API. In the previous examples,Override
and SuppressWarnings
are . It is also possible to define your own annotation type. The Author
and Ebook
annotations in the previous example are custom annotation types.
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