Java反射操作成员变量 Class can not access a member with modifiers "*"

fields[j].set(obj, val);

报：

Exception in thread "main" java.lang.IllegalAccessException: Class pers.hanchao.reflect.fields.ReflectFieldDemo can not access a member of class pers.hanchao.reflect.common.User with modifiers "private"
    at sun.reflect.Reflection.ensureMemberAccess(Reflection.java:102)
    at java.lang.reflect.AccessibleObject.slowCheckMemberAccess(AccessibleObject.java:296)
    at java.lang.reflect.AccessibleObject.checkAccess(AccessibleObject.java:288)
    at java.lang.reflect.Field.get(Field.java:390)
    at 

解决方案：添加一行代码：fields[j].setAccessible(true);