import java.lang.reflect.*;
import java.util.*;
       
public class DynTest {
     public double d; // a field
    
      public int add(int a, int b)
      {
        System.out.println("add() invoked"); 
         return a + b;
      }
      public String tName(String s, Hashtable ht)
      {
        System.out.println("tName() invoked"); 
         return s;
      }
       
      public static void main(String args[])
      {
       //代剛1. Method.invoke()
        {
         try {
                   Class c = Class.forName("DynTest");
            Class pTypes[] = new Class[2];
            pTypes[0] = Integer.TYPE;
            pTypes[1] = Integer.TYPE;
                      Method m = c.getMethod("add", pTypes);
            
                    DynTest obj = new DynTest();
            
                        Object arg[] = new Object[2];
            arg[0] = new Integer(37);
            arg[1] = new Integer(47);
            
                     Object r = m.invoke(obj, arg);
            Integer rVal = (Integer)r;
            System.out.println("return: "+rVal.intValue());  //84
         }
         catch (Throwable e) {
            System.err.println(e);
         }
        }
        
        //代剛2. Method.invoke()
        {
         try {
                       Class c = Class.forName("DynTest");
            Class pTypes[] = new Class[2];
            pTypes[0] = Class.forName("java.lang.String");    
            pTypes[1] = Class.forName("java.util.Hashtable");  
                      Method m = c.getMethod("tName", pTypes);
            
                      Object arg[] = new Object[2];
            arg[0] = new String("return: "+"Hello,World!");
            arg[1] = null;
            
          //ERROR: non-static variable this cannot be referenced from a static context
                      DynTest obj = new DynTest();           
            Object r = m.invoke(obj, arg);
            String rVal = (String)r;
            System.out.println(rVal); //Hello,World!
         }
         catch (Throwable e) {
            System.err.println(e);
         }        
        }
       
        //代剛3. Field.setDouble()
        {
         try {
            Class c = Class.forName("DynTest");
            Field f = c.getField("d");
            DynTest obj = new DynTest();
            System.out.println("before setting, d= " + obj.d); //0.0
            f.setDouble(obj, 12.34);
            System.out.println("after setting, d= " + obj.d);  //12.34
         }
         catch (Throwable e) {
            System.err.println(e);
         }          
        } 
        
      } //main
}