java学习笔记之反射机制

class Demo {
int value;
String name;

Demo() {

}

Demo(String name, int value) {
this.name = name;
this.value = value;
}
public void show(int count){
for (int i = 0; i < count; i++) {
System.out.println(name);
}
}
}

public class reflect {

public static void main(String[] args) throws ClassNotFoundException, IllegalAccessException, InstantiationException, NoSuchMethodException, InvocationTargetException, NoSuchFieldException {
//three ways to get class object
//1
Demo demo=new Demo();
Class clazz1=demo.getClass();

//2
Class clazz2=Demo.class;

//3
Class clazz3=Class.forName("Demo");

//通过类的class对象，调用空参构造函数创建对象
Object obj=clazz1.newInstance();

//通过class的getconstructor（）方法，获取类的构造器对象
Constructor constructor=clazz1.getConstructor(String.class,int.class);
Object obj1=constructor.newInstance("demo111",111);

//通过Field类对该类对象的字段进行操作
Field f1=clazz1.getField("name");//只能获取public的字段
Field f2=clazz2.getDeclaredField("name");//获取所有字段

Object obj2=clazz1.newInstance();
f2.get(obj2);
f2.set(obj,"new name");

//获取并使用类的函数
Method method=clazz1.getMethod("show",int.class);
method.invoke(obj2,3);
}

}