使用Java 5特性来简化反射编程

package org.javalobby.tnt.vararg;
import java.lang.reflect.Method;
public class TestReflectionExample {
public static void main(String[] args) throws Exception {
String s = "Test String";
preJava5(s);
postJava5(s);
}
private static void preJava5(String s) throws Exception {
// First, do a substring
Class c = s.getClass();
Method m = c.getMethod("substring", new Class[] { int.class, int.class });
Object obj = m.invoke(s, new Object[] { new Integer(0), new Integer(4) });
System.out.println(obj);

// Next, do a 'length'
Method m2 = c.getMethod("length", null);
Integer lengthObj = (Integer)m2.invoke(s, null);
int length = lengthObj.intValue();
System.out.println(length);
}
private static void postJava5(String s) throws Exception {
// First, do a substring
Class<?> c = s.getClass();
Method m = c.getMethod("substring", int.class, int.class);
Object obj = m.invoke(s, 0, 4);
System.out.println(obj);
// Next, do a 'length'
Method m2 = c.getMethod("length");
int length = (Integer)m2.invoke(s);
System.out.println(length);  
}
}  

// Pre Java 5
Object obj = m.invoke(s, new Object[] { new Integer(0), new Integer(4) });
// Post Java 5 - Var-args + Autoboxing.
Object obj = m.invoke(s, 0, 4);

// Pre Java-5
Method m2 = c.getMethod("length", null);
Integer lengthObj = (Integer)m2.invoke(s, null);
// Post Java-5. Inferred var-args (no arguments) and auto-unboxing.
Method m2 = c.getMethod("length");
int length = (Integer)m2.invoke(s);

C:\java>java TestReflectionExample
Test
11
Test
11