public class People {
  private String name;
  private int age;
  public People(String name, int age) {
   this.name = name;
    this.age = age;
  }
  public int getAge() {
   return age;
  } 
  public String getName() {
   return name;
  } 
  public void setAge(int age) {
   this.age = age;
  } 
  public void setName(String name) {
   this.name = name;
  }
  public void speak() {
  System.out.println(getName() + " " + getAge());
  }
}

public class Student extends People {
 private int grade;
 public Student(String name, int age) { 
 super(name, age); 
 }
 public Student(String name, int age, int grade) {
 super(name, age);   
 this.grade = grade; 
 }  
 public int getGrade() { 
 return grade; 
 }  
 public void setGrade(int grade) { 
 this.grade = grade; 
 } 
 private void learn(String course) { 
 System.out.println(name + " learn " + course); 
 }
}

Class<People> peopleClass = People.class;

//假设People类在com.test包中
Class<People> peopleClass = Class.forName("com.test.People");

People people = new People("Bill"， 18);
Class<People> peopleClass = people.getClass();

public static void main(String[] args) { 
 Class<People> pClass = People.class; 
 try { 
 Constructor<People> constructor = pClass.getConstructor(String.class, int.class);  
 People people = constructor.newInstance("Bill", 18);     
 obj.speak(); 
 } catch (Exception e) { 
 } 
}

Constructor<People> constructor = peopleClass.getConstructor(String.class， 
 int.class);
// 设置 constructor 的 Accessible属性为ture以取消Java的访问检查
constructor.setAccessible(true);

private static void showDeclaredMethods() { 
 Student student = new Student("Bill", 18); 
 //获取Student类声明的所有方法 
 Method[] methods = student.getClass().getDeclaredMethods();  
 try {  
  //获取learnMethod对象（封装了learn方法） 
  Method learnMethod = student.getClass().getDeclaredMethod("learn", 
   String.class);    
  //获取learn方法的参数列表并打印出来 
  Class<?>[] paramClasses = learnMethod.getParameterTypes() ;  
  for (Class<?> class : paramClasses) {  
  System.out.println("learn方法的参数: " + class.getName()); 
  }    
  //判断learn方法是否为private 
  System.out.println(learnMethod.getName() + " is private " 
   + Modifier.isPrivate(learnMethod.getModifiers())); 
  //调用learn方法 
  learnMethod.invoke(student, "Java Reflection"); 
 } catch (Exception e) { 
 }
}

private static void showMethods() { 
 Student student = new Student("mr.simple"); 
 // 获取所有public方法(包括Student本身的和从父类继承来的） 
 Method[] methods = student.getClass().getMethods(); 
 try { 
 //注意，通过 getMethod只能获取public方法，若尝试获取private方法则会抛出异常 
 Method learnMethod = student.getClass().getMethod("learn", String.class);
 } catch (Exception e) { 
 }
}

private static void showDeclaredFields() { 
 Student student = new Student("Bill", 18); 
 // 获取当前类中定义的所有属性 
 Field[] fields = student.getClass().getDeclaredFields(); 
 try { 
 // 获取指定的属性 
 Field gradeField = student.getClass().getDeclaredField("grade"); 
 // 获取属性值 
 System.out.println("The grade is : " + gradeField.getInt(student)); 
 // 设置属性值 
 gradeField.set(student, 10); 
 } catch (Exception e) { 
 } 
}

private static void showFields() { 
 Student student = new Student("Bill"， 18);   
 // 获取当前类和父类的所有public属性 
 Field[] publicFields = student.getClass().getFields();  
}

Student student = new Student("Bill", 18);
Class<?> superClass = student.getClass().getSuperclass();

private static void showInterfaces() { 
 Student student = new Student("Bill", 19); 
 Class<?>[] interfaces = student.getClass().getInterfaces();
}