创建运行时类的对象，调用指定的属性方法构造器

1 使用newInstance(),实际上是调用运行时空参的构造器

   注意构造器的权限修饰符要足够，同时必须有一个空参的构造器。

2 调用指定的属性方法构造器

package lianxi1;

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

import org.junit.Test;



public class TestReflection2 {
    @Test
    public void test1() throws ClassNotFoundException, SecurityException, NoSuchFieldException, InstantiationException, IllegalAccessException {
        //1.获取运行类的属性
        String str = "lianxi1.Person";
        Class clazz = Class.forName(str);
        Field f1 = clazz.getField("name");
        //如果属性是private的
        Field f2 = clazz.getDeclaredField("age");
        f2.setAccessible(true);
       //2.创建运行类的对象
        Object obj = clazz.newInstance();
        Person p = (Person)obj;
        System.out.println(p);
       //3.对属性赋值
        f1.set(p, "tian");
        f2.set(p, 25);
        System.out.println(p);
    }
    @Test
    public void test2() throws ClassNotFoundException, SecurityException, NoSuchMethodException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException{
        //2.调用运行时类中指定的方法
        Class clazz = Person.class;
        Method m1 = clazz.getMethod("show");
        Person p1 = (Person)clazz.newInstance();
        Object obj = m1.invoke(p1);   //如果是静态方法改为 m1.invoke(Person.class)
        System.out.println(obj);
        
        Method m2 = clazz.getDeclaredMethod("display",String.class,int.class);
        m2.setAccessible(true);
        Object obj2 = m2.invoke(p1,"yu",22);
        System.out.println(obj2);
    }
    @Test
    public void test3() throws SecurityException, NoSuchMethodException, IllegalArgumentException, InstantiationException, IllegalAccessException, InvocationTargetException{
        //3.调用制定的构造器，创建运行时类的对象
        Class clazz = Person.class;
        Constructor con = clazz.getDeclaredConstructor(String.class,int.class);
        con.setAccessible(true);
        Person p2 = (Person)con.newInstance("wuming",21);
        System.out.println(p2);
        
    }
}