类型检查

Ø 静态检查：类型types

    动态检查：值values

Ø Java和许多其他编程语言中的一个点是 它的原始数值类型有特例， 表现得不像我们习惯的整数和实数。因此，应该动态检查一些错误 根本不检查。

– Integer division: 5/2 does not return a fraction, it returns a truncated

integer.

– Integer overflow. If the computation result is too positive or too negative

to fit in that finite range, it quietly overflows and returns a wrong answer.

(no static / dynamic checking!) e.g., int big = 200000*200000;

– Special values in floating-point types. NaN (“Not a Number”),

POSITIVE_INFINITY, and NEGATIVE_INFINITY. e.g., double a=7/0;