类反射得到类的属性，方法和构造器

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Member;
import static java.lang.System.out;

enum ClassMember {
    CONSTRUCTOR, FIELD, METHOD, CLASS, ALL
}

public class ClassSpy {
    public static void main(String... args) {
        try {
            Class c = Class.forName(args[0]);
            out.format("Class:%n  %s%n%n", c.getCanonicalName());

            Package p = c.getPackage();
            out.format("Package:%n  %s%n%n", (p != null ? p.getName()
                    : "-- No Package --"));

            for (int i = 1; i < args.length; i++) {
                switch (ClassMember.valueOf(args[i])) {
                case CONSTRUCTOR:
                    printMembers(c.getConstructors(), "Constructor");
                    break;
                case FIELD:
                    printMembers(c.getFields(), "Fields");
                    break;
                case METHOD:
                    printMembers(c.getMethods(), "Methods");
                    break;
                case CLASS:
                    printClasses(c);
                    break;
                case ALL:
                    printMembers(c.getConstructors(), "Constuctors");
                    printMembers(c.getFields(), "Fields");
                    printMembers(c.getMethods(), "Methods");
                    printClasses(c);
                    break;
                default:
                    assert false;
                }
            }

            // production code should handle these exceptions more gracefully
        } catch (ClassNotFoundException x) {
            x.printStackTrace();
        }
    }

    private static void printMembers(Member[] mbrs, String s) {
        out.format("%s:%n", s);
        for (Member mbr : mbrs) {
            if (mbr instanceof Field)
                out.format("  %s%n", ((Field) mbr).toGenericString());
            else if (mbr instanceof Constructor)
                out.format("  %s%n", ((Constructor) mbr).toGenericString());
            else if (mbr instanceof Method)
                out.format("  %s%n", ((Method) mbr).toGenericString());
        }
        if (mbrs.length == 0)
            out.format("  -- No %s --%n", s);
        out.format("%n");
    }

    private static void printClasses(Class c) {
        out.format("Classes:%n");
        Class[] clss = c.getClasses();
        for (Class cls : clss)
            out.format("  %s%n", cls.getCanonicalName());
        if (clss.length == 0)
            out.format("  -- No member interfaces, classes, or enums --%n");
        out.format("%n");
    }
}