To find out what public methods belong to a class, invoke
the method named getMethods. The array
returned by getMethods contains
Method 
objects. You can use a Method
object to uncover a method's name, return type, parameter types, set of
modifiers, and set of throwable exceptions. All of this information would be
useful if you were writing a class browser or a debugger.
With Method.invoke, you can even call the method itself.
To see how to do this, see the section
Invoking Methods.
The following sample program prints the name, return type, and parameter types of
every public method in the Polygon class. The program
performs the following tasks:
-
It retrieves an array of
Method objects from the
Class object by calling getMethods.
-
For every element in the
Method array,
the program:
-
retrieves the method name by calling
getName
-
gets the return type by invoking
getReturnType
-
creates an array of
Class objects by invoking
getParameterTypes
-
The array of
Class objects created in
the preceding step represents the parameters
of the method.
To retrieve the class name for every one of these parameters,
the program invokes getName against each
Class object in the array.
Not many lines of source code are required to accomplish these
tasks:
import java.lang.reflect.*;
import java.awt.*;
class SampleMethod {
public static void main(String[] args) {
Polygon p = new Polygon();
showMethods(p);
}
static void showMethods(Object o) {
Class c = o.getClass();
Method[] theMethods = c.getMethods();
for (int i = 0; i < theMethods.length; i++) {
String methodString = theMethods[i].getName();
System.out.println("Name: " + methodString);
String returnString =
theMethods[i].getReturnType().getName();
System.out.println(" Return Type: " + returnString);
Class[] parameterTypes = theMethods[i].getParameterTypes();
System.out.print(" Parameter Types:");
for (int k = 0; k < parameterTypes.length; k ++) {
String parameterString = parameterTypes[k].getName();
System.out.print(" " + parameterString);
}
System.out.println();
}
}
}
An abbreviated version of the output generated by the sample program
is as follows:
Name: equals
Return Type: boolean
Parameter Types: java.lang.Object
Name: getClass
Return Type: java.lang.Class
Parameter Types:
Name: hashCode
Return Type: int
Parameter Types:
.
.
.
Name: intersects
Return Type: boolean
Parameter Types: double double double double
Name: intersects
Return Type: boolean
Parameter Types: java.awt.geom.Rectangle2D
Name: translate
Return Type: void
Parameter Types: int int
