程序员修炼之道

 一 资源的配平：有始有终，

对于多种资源需求

1 释放的顺序与分配的顺序相反，以防止资源浪费。

2 总是以相同的顺序分配资源，防止死锁。

 二 配平与异常：

异常会打乱程序的正常执行逻辑，从而打乱资源配平原。如何处理取决于语言。

在c++中：

try {

 　　//....

  　Node *n= new Node;

}catch {

delete n;

throw ;

}

delete n;

重复删除 违反DRY，so 利用局部对象退出包含块时会被自动清除，you can change it to be a object contain a point .

在java 有GC,and finally ,but i don't know why GC can't fix it  alone?is it necessary to add the finally statement ?

三 无法配平

程序中确实需要某一块长期存在的动态内存块，SO HOW TO FIX ?

there must be a top block to manage the memory,then we have 3 choices to free it.

3 choices:

1 make a recursion to free it from top to bottom.

2 just free itself ,and disert its children rudely.

3 free itself ,and chilldren manage itself.

answer to prectice.

in c++ and java when you free  a point ,why make p = null ? is there differences between them?

1 c++ in case of wild point.p == null is a running error,so it is possible to be checked.

2  java  :it is convenience for garbage collection, p = null means the count of the object which p point at --,when p = 0,gc begint to finish it;

二

how to make couple minimize between modules?

(Principal of) Least Knowledge，(The) Law of Demeter。

what is exactly it ?

don't talk with stranger .in the method you just access method directly by stack/heap object  created inside it,the member of class ,and arguments .

if you wanna use the method in the third class ,you can access it by the second class .of cause you need to package the interface in the second one.