Annotations in Java

Annotations provide information to a program, but are not part of the program itself. Annotations have the following uses:

* Provides information to compilers, equivalent to precompiled directives in the C language

* Deployment-time processing, software tools can generate code based on annotations, XML files and so on, such as writing servlets, without changing the Web. XML, only need to use annotations.

* Run-time processing, some annotations can be checked at run time.

Example: @SuppressWarnings (value= "unchecked")

If there is only one element and its name is value, you can omit the name and write the value directly

Example: @SuppressWarnings ("unchecked")

If there are no elements, you can omit the parentheses

Example: @Override

defining annotation Types

@Interface  classpreamble {    String author ();    String date ();     int default 1;     default "2014-3-32";    String[] Reviewers ();} @ClassPreamble (Author= "Weidiao", date= "2014-3-23", reviewers = {"}")class  weidiao{    }

There are three types of annotations used by the compiler: @Deprecated, @Override, @SuppressWarnings

Annotations in Java