参考官方文档：https://www.jetbrains.com/help/idea/symbols.html#common-icons
自己常用的列在下面：
图标上有灰边边的是抽象的，比如抽象类、方法
| Icon | Description |
|---|---|
 |
Class |
 |
Abstract class |
 |
Groovy class |
 |
Annotation |
 |
Enumeration |
 |
Exception |
 |
Final Java class |
 |
Interface |
 |
Java class that contains declaration of the main() method. |
 |
Test case |
 |
Method |
 |
Abstract method |
 |
Field |
 |
Variable（可能是基本数据类型或者引用数据类型） |
 |
Property |
 |
Parameter |
 |
Element |
| Project structure | |
 |
Directory |
 |
Module |
 |
Group of modules |
 |
Package |
 |
Sources root |
 |
Test root |
 |
Excluded root |
 |
Resources |
 |
Test resources |
 |
Generated sources root |
 |
Generated test sources root |
| Visibility modifiers | |
 |
Read-only class, for example from a jar of an external library. |
 |
private |
 |
protected |
 |
package protected |
 |
static |
 |
public |