Reflection - The Java Programming Language - page 617

16.6. The Field Class
The Field class defines methods for asking the type of a field and for set-
ting and getting the value of the field. Combined with the inherited Member
methods, this allows you to find out everything about the field declara-
tion and to manipulate the field of a specific object or class.
The getGenericType method returns the instance of Type that represents
the field's declared type. For a plain type, such as String or int , this
returns the associated Class object String.class and int.class , respect-
ively. For a parameterized type like List<String> , it will return a Paramet-
erizedType instance. For a type variable like T , it will return a TypeVariable
instance.
The getType legacy method returns the Class object for the type of the
field. For plain types this acts the same as getGenericType . If the field's
declared type is a parameterized type, then getType will return the class
object for the erasure of the parameterized typethat is, the class object
for the raw type. For example, for a field declared as List<String> , getType
will return List.class . If the field's declared type is a type variable, then
getType will return the class object for the erasure of the type variable.
For example, given class Foo<T> , for a field declared with type T , getType
would return Object.class . If Foo were declared as Foo<Textends Number> ,
then getType would return Number.class .
You can ask whether a field is an enum constant using isEnumConstant .
You can also get and set the value of a field using the get and set meth-
ods. There is a general-purpose form of these methods that take Object
arguments and return Object values, and more specific forms that deal
directly with primitive types. All of these methods take an argument spe-
cifying which object to operate on. For static fields the object is ignored
and can be null . The following method prints the value of a short field of
an object:
public static void printShortField(Object o, String name)
throws NoSuchFieldException, IllegalAccessException
{