反射

Reflection

A way for a program/application to learn about itself, change itself, and perhaps even add to itself.

//获取className的三种方法

Datedate=newDate();

Class<?>clazz=date.getClass();

Class<?>clazz1=Date.class();

Class<?>clazz2=Class.forName("java.lang.Object");

/**

  * java.lang.Class

  * The java.lang.Class class instance represent classes and interfaces in a running Java application.

  */

​

//运行时创建对象,传参数和不传参数

//Class.newInstance();

Class<?>clazz=Class.forName("cn.tju.scs.c03.reflection.CarRef");

Objectobj=clazz.newInstance();

​

//Constructor.newInstance(para1,para2);

Constructor<?>con=clazz.getConstructor(String.class,double.class);

Objectobj=con.newInstance("大众",20.3);

//invoke method

Classclazz=Teacher.class;

Personteacher=newTeacher();

Methodm0=clazz.getMethod("toString");

//参数不同 名字相同overload

Methodm1=clazz.getMethod("eat",String.class);

Methodm2=clazz.getMethod("eat",String.class,int.class);​

​

m0.invoke(teacher);

//改变变量

Class<?>clazz=Class.forName("cn.tju.scs.c03.reflection.CarMethod");

Objectobj=clazz.newInstance();

FieldnameField=clazz.getDeclaredField("name");

​

nameField.setAccessible(true);

nameField.set(obj,"红旗");

When a method in a Class will be invoked?

– Reflection

– Clone

– New