Whenever you are writing OOP, basic thing you will do is to create many types and create instances of the types in other classes. And unless we import the types in the code, you will see unresolved references error. Instead of resolving each unresolved references, you can press CTRL+SHIFT+O that is a short cut for organize imports in Spring STS or any eclipse based tool. If you are working on Mac like me then the shortcut is COMMAND+SHIFT+O.