Java Examples in a Nutshell, 3rd Edition

Obtaining Class and Member Information

Example 9-1 shows a program that uses the Class, Constructor, Field, and Method classes to display information about a specified class. The program’s output is similar to the class synopses that appear in Java in a Nutshell. (You might notice that the names of method arguments are not shown; argument names are not stored in class files, so they are not available through the Reflection API.)

Here is the output from using ShowClass on itself:

public class ShowClass extends Object {
  // Constructors
  public ShowClass( );
  // Fields
  // Methods
  public static void main(String[  ]) throws ClassNotFoundException;
  public static String modifiers(int);
  public static void print_class(Class);
  public static String typename(Class);
  public static void print_field(Field);
  public static void print_method_or_constructor(Member);
}

The code for this example is quite straightforward. It uses the Class.forName( ) method to dynamically load the named class, and then calls various methods of the Class object to look up the superclass, interfaces, and members of the class. The example uses Constructor, Field, and Method objects to obtain information about each member of the class.

Example 9-1. ShowClass.java

package je3.reflect; import java.lang.reflect.*; /** A program that displays a class synopsis for the named class */ public class ShowClass { /** The main method. Print info about the named class */ public static void main(String[ ] args) throws ClassNotFoundException ...