Java如何基于反射机制获取不同的类

public class MyReflect {
  public static void main(String[] args) throws ClassNotFoundException {
    Teacher t = new Teacher();
    // 1、通过对象获得
    Class c1 = t.getClass();
    // 2、forName + 全限定名 获得
    Class c2 = Class.forName("reflect.Teacher");
    // 3、通过类名获得
    Class c3 = Teacher.class;
    // 4、基本数据类型的Type属性获得
    Class c4 = Double.TYPE;
    // 5、通过子类的Class对象获得
    Class c5 = c1.getSuperclass();
  }
}
class Person {
  String name;
  public Person() {
  }
}
class Teacher extends Person {
  public Teacher() {
  }
}

package reflect;

class Person {
  public String name;
  private int age;

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }

  public int getAge() {
    return age;
  }

  public void setAge(int age) {
    this.age = age;
  }

  public Person() {
  }

  public Person(String name, int age) {
    this.name = name;
    this.age = age;
  }

  @Override
  public String toString() {
    return "Person{" +
        "name='" + name + '\'' +
        ", age=" + age +
        '}';
  }

  public String greet(String name) {
    return "hello " + name + ".";
  }
}

class Teacher extends Person {

}

public class MyConstructor {
  public static void main(String[] args) throws Exception {
    Class<Person> c = (Class<Person>) Class.forName("reflect.Person");

//    Object person2 = c.newInstance();  //@Deprecated
//    System.out.println(person2);
    Constructor<Person> constructor = c.getConstructor();
    Person person = constructor.newInstance();
    System.out.println(person);

    // 获取 public 有参构造方法
    Constructor<Person> constructor1 = c.getConstructor(String.class, int.class);
    Person person1 = constructor1.newInstance("JL", 18);
    System.out.println(person1);

    // 获取构造方法
    Constructor<Person> constructor2 = c.getDeclaredConstructor(String.class, int.class);
    constructor2.setAccessible(true);
    Person person2 = constructor1.newInstance("JL", 18);
    System.out.println(person2.name);
  }
}

public class MyField {
  public static void main(String[] args) throws Exception {
    Class<?> c = Class.forName("reflect.Person");
    // 在Person类中，无参的构造方法不能省略
    Object p = c.getConstructor().newInstance();

    // 获取 public 成员变量
    Field[] fields = c.getFields();
    // 获取所有成员变量（包括 private)
    Field[] allFields = c.getDeclaredFields();
    //获取指定名称public变量
    Field f1 = c.getField("name");
    // 成员变量set、get
    f1.set(p, "JL");
    System.out.println(f1.get(p));

    Field f2 = c.getDeclaredField("age");  // private int age
    // 忽略权限检查，使得 private 成员可以被访问
    f2.setAccessible(true);
    f2.set(p, 18);
    System.out.println(f2.get(p));
  }
}

 public class MyMethod {
   public static void main(String[] args) throws Exception {
     Class<Person> c = (Class<Person>) Class.forName("reflect.Person");
     Person p = c.getConstructor().newInstance();
     // 获取所有 public 方法
     Method[] methods = c.getMethods();
     // 获取 greet 方法
     Method method1 = c.getMethod("greet", String.class);
     //执行 greet 方法
     System.out.println(method1.invoke(p, "JL"));
   }
 }
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