public class Person {
    private String name;
    public int age;
    public String nation;

    public Person() {
    }

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

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

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

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

    public String getNation() {
        return nation;
    }

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

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

    public void setNation(String nation) {
        this.nation = nation;
    }

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", nation='" + nation + '\'' +
                '}';
    }
    public void show() {
        System.out.println(this);
    }
}

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

public class ReflectTest {
    public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException, InvocationTargetException, NoSuchMethodException, NoSuchFieldException {
//        Person p1 = new Person("Tom", 12, "中国");

        //通过反射，创建运行时类对象
        Class clazz = Person.class;// or Class<Person> clazz = Person.class;
        Constructor cons = clazz.getConstructor(String.class, int.class);
        Person p1 = (Person) cons.newInstance("Tom", 14);
        System.out.println(p1);
        //getConstructors(): 获取当前运行时类中声明为public的构造器（不包含父类构造器）
        Constructor[] constructors = clazz.getConstructors();
        for (Constructor c: constructors) {
            System.out.println(c);
        }
        //getDeclaredConstructors(): 获取当前运行时类中声明的所有构造器
        Constructor[] declaredConstructors = clazz.getDeclaredConstructors();
        for (Constructor c: declaredConstructors) {
            System.out.println(c);
        }


        //getFields(): 获取当前运行时类及其父类中声明为public访问权限的属性
        Field[] fields = clazz.getFields();
        for (Field f: fields) {
            System.out.println(f);
        }
        //getDeclaredFields(): 获取当前运行时类中声明的所有属性（不包含父类）
        Field[] declaredFields = clazz.getDeclaredFields();
        for (Field f: declaredFields) {
            System.out.println(f);
        }
        //getDeclaredField(属性名称): 通过反射，调用对象指定的属性
        Field age = clazz.getDeclaredField("age");
        if(!age.isAccessible()) {
            age.setAccessible(true);//设置为可访问，否则私有属性不可访问
        }
        age.set(p1, 10);
        System.out.println(p1);


        //getMethods(): 获取当前运行时类及其父类中声明为public访问权限的方法
        Method[] methods = clazz.getMethods();
        for (Method method: methods) {
            System.out.println(method);
        }
        //getDeclaredMethods(): 获取当前运行时类中声明的所有方法（不包含父类）
        Method[] declaredMethods = clazz.getDeclaredMethods();
        for (Method method: declaredMethods) {
            System.out.println(method);
        }
        //getDeclaredMethod(方法名称): 通过反射，调用对象指定的方法
        Method show = clazz.getDeclaredMethod("show");
        if(!show.isAccessible()){
            show.setAccessible(true);//设置为可访问，否则私有方法不可访问
        }
        show.invoke(p1);


        //获取类实例的4种方式
        //方式一：.class（有限制：编译时就把要调用的类名确定了）
        Class clazz1 = Person.class;
        System.out.println(clazz1);//class reflectTest.Person
        //方式二：通过运行时类对象（有限制：提前是本身就有该类的对象）
        Person p = new Person("Tom", 12);
        Class clazz2 = p.getClass();
        System.out.println(clazz2);//class reflectTest.Person
        //方式三：调用class的静态方法（常用）
        Class clazz3 = Class.forName("reflectTest.Person");
        System.out.println(clazz3);//class reflectTest.Person
        //方式四：使用类的加载器：ClassLoader（不常用）
        ClassLoader classLoader = ReflectTest.class.getClassLoader();
        Class clazz4 = classLoader.loadClass("reflectTest.Person");
        System.out.println(clazz4);//class reflectTest.Person
    }
}