参考资料：
1、http://blog.****.net/itdada/article/details/43375893
常用设置：
1.Tab不用4个空格
Code Style->Java->Tabs and Indents->Use tab character
Code Style->General->Use tab character （例如：版本控制Diff界面按下Tab）
2.可视化Tab和空格
Settings->IDE Settings->Editor->Appearance->Show whitespaces
3.显示代码行数
Settings->IDE Settings->Editor->Appearance->Show line numbers
4.修改代码字体大小
Settings->IDE Settings->Editor->Colors & Fonts ->Font->Save As->改个名字后才能改字体大小
5.鼠标悬浮显示doc
Settings->IDE Settings->Editor->Show quick doc on mouse move
6.空行的Tab和空格被自动干掉
Settings->IDE Settings->Editor->Other->Strip trailing spaces on Save->None