[1.List转换成为数组。(这里的List是实体是ArrayList) 　　调用ArrayList的toArray方法。　　toArray　　public T[] toArray(T[] a)返回一个按照正确的顺序包含此列表中

INCLUDE_DIRECTORIES: Add include directories to the build.[            最近在学习Linux下的C编程，买了一本叫《Linux环境下的C编程指南》读到makefile就越看越迷糊，可能是我的理解能不行。            于是google到了以下这篇文

INCLUDE_DIRECTORIES([AFTER|BEFORE] [SYSTEM] dir1 dir2 ...)

Add the given directories to those searched by the compiler for include files. By default the directories are appended onto the current list of directories. This default behavior can be changed by setting CMAKE_INCLUDE_DIRECTORIES_BEFORE to ON. By using BEFORE or AFTER you can select between appending and prepending, independent from the default. If the SYSTEM option is given the compiler will be told that the directories are meant as system include directories on some platforms.[一般报java.lang.NullPointerException的原因有以下几种： ·字符串变量未初始化； ·接口类型的对象没有用具体的类初始化，比如： List lt; 会报错 List lt = new ArrayL