1.Check Parameters
参数检查
–Don’t trust the inputs
–Fail quickly and cleanly
–Document exceptions that will be thrown including unchecked exceptions
-For unexported (non-public) methods, assert the validity of parameters
2.Exceptions are not for control flow
*异常仅用于例外情况，尽量使用标准异常库
-Exceptions should never be used for ordinary control flow
-Well-designed APIs do not force clients to program to exceptions
3.Cater for client assumptions
-Return empty arrays or collections, not nulls
4.Defensive copying
对于每个可变参数的赋值和构造进行防御性拷贝
-Make defensive copies when needed
*Perform defensive copying before checking validity
*For get methods, return defensive copies of mutable internal fields
5.Immutability
原文：http://www.cnblogs.com/eli-ayase/p/5281971.html