求一个利用java反射的例子

不太理解反射的作用

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Java code:
import java.lang.reflect.*;
public class ReflectionTest {
public static void main(String[] args) {
Class c=null;
try {
c=Class.forName("java.lang.String");
System.out.println("package "+c.getPackage().getName()+";");
System.out.print(Modifier.toString(c.getModifiers())+" ");
System.out.print("class "+c.getSimpleName()+" ");
if (c.getSuperclass()!=Object.class) {
System.out.print("extends " + c.getSuperclass().getSimpleName());
}
Class[] inters=c.getInterfaces();
if(inters.length>0){
System.out.print("implements ");
for(int i=0;i<inters.length;i++){
System.out.print(inters[i].getSimpleName());
if(i<inters.length-1){
System.out.print(",");
}
}
}
System.out.println("{");
printFields(c);
printMethods(c);
System.out.println("}");
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}