ReflectionTest:由输入的类名得到类的信息

 package reflection;

 import java.lang.reflect.*;
 import java.util.*;

 public class ReflectionTest {
     public static void main(String[] args)
     {
         String name;
         if(args.length>0) name =args[0];
         else
         {
             Scanner in = new Scanner(System.in);
             System.out.println("Enter class name (e.g. java.util.Date):");
             name = in.next();
         }
         try
         {
             Class cl = Class.forName(name);
             Class supercl = cl.getSuperclass();
             String modifiers = Modifier.toString(cl.getModifiers());
             if (modifiers.length() > 0) System.out.print(modifiers + " ");
             System.out.print("class " + name);
             if (supercl != null && supercl != Object.class) System.out.print(" extends " + supercl.getName());

             System.out.print("\n{\n");
             printConstructors(cl);
             System.out.println();
             printMethods(cl);
             System.out.println();
             printFields(cl);
             System.out.println("}");

         }
         catch (ClassNotFoundException e)
         {
             e.printStackTrace();
         }
         System.exit(0);
     }
     public static void printConstructors(Class cl)
     {
         Constructor[] constructors = cl.getDeclaredConstructors();
         for(Constructor c:constructors)
         {
             String name = c.getName();
             System.out.print("   ");
             String modifiers = Modifier.toString(c.getModifiers());
             if(modifiers.length()>0) System.out.print(modifiers+" ");
             System.out.print(name+"(");

             Class[] paramTypes = c.getParameterTypes();
             for (int j=0; j<paramTypes.length; j++)
             {
                 if(j>0) System.out.print(", ");
                 System.out.print(paramTypes[j].getName());
             }
             System.out.println(");");
         }
     }

     public static void printMethods(Class cl)
     {
         Method[] methods = cl.getDeclaredMethods();

         for(Method m:methods)
         {
             Class retType = m.getReturnType();
             String name  = m.getName();

             System.out.print("   ");
             String modifiers = Modifier.toString(m.getModifiers());
             if(modifiers.length()>0) System.out.print(modifiers+" ");//private static final都是修饰符
             System.out.print(retType.getName()+" "+name + "(");

             Class[] paramTypes = m.getParameterTypes();//获取一个方法的所有参数
             for(int j=0;j<paramTypes.length;j++)
             {
                 if(j>0) System.out.print(", ");
                 System.out.print(paramTypes[j].getName());//获取一个参数的类型
             }
             System.out.println(");");
         }
     }

     public static void printFields(Class cl)
     {
         Field[] fields = cl.getDeclaredFields();

         for(Field f:fields)
         {
             Class type = f.getType();
             String name = f.getName();
             System.out.print("   ");
             String modifiers = Modifier.toString(f.getModifiers());
             if(modifiers.length()>0) System.out.print(modifiers+" ");
             System.out.println(type.getName()+" "+ name +";");

         }
     }

 }