final—修饰符（关键字）如果一个类被声明为final，意味着它不能再派生出新的子类，不能作为父类被继承。因此一个类不能既被声明为 abstract的，又被声明为final的。将变量或方法声明为final，可以保证它们在使用中不被改变。被声明为final的变量必须在声明时给定初值，而在以后的引用中只能读取，不可修改。被声明为final的方法也同样只能使用，不能重载-final-modifier (keyword) if a class was declared to be final, means that it should not send another gives rise to new sub-category, as a parent should not be inherited. Therefore a class should not be a statement not only for the abstract, and it was a statement for the final. The variable or method statement for the final, can ensure that they are not in use change. Was a statement for the final variable must be given in a statement when the initial value, and in subsequent references only read, can not be amended. Was a statement for the final approach can only use the same can not be overloaded