反射（变量）

加载字节码文件，获取Class类对象

Class cls = Class.forName("com.qfedu.a_reflect.Person");

获取所有用public修饰的成员变量

Field[] allPublicFields = cls.getFields();

for (Field field : allPublicFields) {

System.out.println(field);

}

获取所有的成员变量

Field[] allFields = cls.getDeclaredFields();

for (Field field : allFields) {

System.out.println(field);

}

Field aPublicField = cls.getField("test");

System.out.println(aPublicField);

set方法

//set(Oject obj, Object value);

//第一个参数: 要操作的是哪一个对象里面的成员变量

//第二个参数: 需要设置的值

Person p = (Person) cls.getConstructor(int.class, String.class).

newInstance(1, "狗蛋");

aPublicField.set(p, 20);

System.out.println("44" + p.test);

System.out.println("$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$");

Field aStaticField = cls.getField("testStatic");

System.out.println(aStaticField);

aStaticField.set(null, 20);

System.out.println(Person.testStatic);

System.out.println("$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$");

Field aPrivateField = cls.getDeclaredField("id");

System.out.println(aPrivateField);

aPrivateField.setAccessible(true);

aPrivateField.set(p, 10);

System.out.println(p.getId());