1  import java.lang.reflect.*;

  2  import java.util.*;

  3  

  4  /**

  5     This program shows how to use reflection to print

  6     the names and values of all nonstatic fields of an object.

  7  */

  8  public class FieldTester

  9  {

 10     public static void main(String[] args)

 11           throws IllegalAccessException

 12     {

 13        Random r = new Random();

 14        System.out.print(spyFields(r));

 15        r.nextInt();

 16        System.out.println("\nAfter calling nextInt:\n");      

 17        System.out.print(spyFields(r));

 18     }

 19  

 20     /**

 21        Spies on the field names and values of an object.

 22        @param obj the object whose fields to format

 23        @return a string containing the names and values of

 24        all fields of obj

 25     */

 26     public static String spyFields(Object obj)

 27           throws IllegalAccessException

 28     {

 29        StringBuffer buffer = new StringBuffer();

 30        Field[] fields = obj.getClass().getDeclaredFields();

 31        for (Field f : fields)

 32        {

 33           if (!Modifier.isStatic(f.getModifiers()))

 34           {

 35              f.setAccessible(true);

 36              Object value = f.get(obj);

 37              buffer.append(f.getType().getName());

 38              buffer.append(" ");

 39              buffer.append(f.getName());

 40              buffer.append("=");

 41              buffer.append("" + value);

 42              buffer.append("\n");

 43           }

 44        }

 45        return buffer.toString();

 46     }

 47  }