反射

//打印类中的所有方法
public static void main(String[] args) throws ClassNotFoundException {
    String className = "java.util.Scanner";
   Class<?> cl = Class.forName(className);
   while (cl != null){
       for (Method m:cl.getDeclaredMethods()){
           System.out.println(
               Modifier.toString(m.getModifiers()) + " " +
                   m.getReturnType().getCanonicalName() + " " +
                   m.getName() +
                   Arrays.toString(m.getParameters())
           );
       }
       cl = cl.getSuperclass();
   }

//打印类中的所有字段

public static void main(String[] args) throws ClassNotFoundException, IllegalAccessException {
    People p1 = new People();
    p1.setName("张三");
    p1.setAge(30);
    printField(p1);

    People p2 = new People();
    p2.setName("李四");
    p2.setAge(3);
    printField(p2);
}
private static void printField(Object obj) throws IllegalAccessException {
    for (Field f : obj.getClass().getDeclaredFields()) {
        f.setAccessible(true);
        Object value = f.get(obj);
        System.out.println(f.getName() + ":" + value);
    }
}