Java Reference
In-Depth Information
Each of these reflection classes has methods for working with an element of a class.
A
Method
object holds information about a single method in a class. To find out about
all methods contained in a class, create a
Class
object for that class and call
getDeclaredMethods()
on that object. An array of
Method[]
objects is returned that rep-
resents all methods in the class not inherited from a superclass. If no methods meet that
description, the length of the array is 0.
The
Method
class has several useful instance methods:
getParameterTypes()
—This method returns an array of
Class
objects represent-
ing each argument contained in the method signature.
n
getReturnType()
—This method returns a
Class
object representing the return
type of the method, whether it's a class or primitive type.
n
getModifiers()
—This method returns an
int
value that represents the modifiers
that apply to the method, such as whether it is
public
,
private
, and the like.
n
Because the
getParameterTypes()
and
getReturnType()
methods return
Class
objects,
you can use
getName()
on each object to find out more about it.
The easiest way to use the
int
returned by
getModifiers()
is to call the
Modifier
class
method
toString()
with that integer as an argument. For example, if you have a
Method
object named
current
, you can display its modifiers with the following code:
int mods = current.getModifiers();
System.out.println(Modifier.toString(mods));
The
Constructor
class has some of the same methods as the
Method
class, including
getModifiers()
and
getName()
. One method that's missing, as you might expect, is
getReturnType()
; constructors do not contain return types.
To retrieve all constructors associated with a
Class
object, call
getConstructors()
on
that object. An array of
Constructor
objects is returned.
To retrieve a specific constructor, first create an array of
Class
objects that represent
every argument sent to the constructor. When this is done, call
getConstructors()
with
that
Class
array as an argument.
For example, if there is a
KeyClass(
String
,
int
)
constructor, you can create a
Constructor
object to represent this with the following statements:
Class kc = KeyClass.class;
Class[] cons = new Class[2];
cons[0] = String.class;
