Java反射 java.lang.NoSuchMethodException

Question

 public static void testTT() throws Exception {
        Class<?> clazz = Class.forName("reflect.Person");
        // 获得构造器
        Constructor<?> constructor = clazz.getDeclaredConstructor(new Class[] {});
        // 根据类的默认构造器来获得一个对象
        Object instance = constructor.newInstance(new Object[] {});
        System.out.println(instance);

        Constructor<?> constructor2 = clazz
                .getDeclaredConstructor(new Class[] { Integer.class, String.class, Integer.class });
        Object instance2 = constructor2.newInstance(new Object[]{1,"Tom",21});
        System.out.println(instance2);
    }

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

 Exception in thread "main" java.lang.NoSuchMethodException: reflect.Person.<init>(java.lang.Integer, java.lang.String, java.lang.Integer)
    at java.lang.Class.getConstructor0(Unknown Source)
    at java.lang.Class.getDeclaredConstructor(Unknown Source)

Answer 1

Constructor<?> constructor2 = clazz.getDeclaredConstructor(new Class[] { int.class, String.class, int.class });