Each arithmetic operation on any of those types results in an int result,which must be explicitly cast back to the original type (a narrowing conversion that might lose information) to assign back to that type.

• 对这些类型的任何一个进行算术运算，都会获得一个int结果。必须将其明确“造型”回原来的类型(缩小转换会造成信息的丢失)，以便将值赋回那个类型。