From FDT Documentation

During the course of writing code, either you will need to import an object into your class or unused imports will accumulate. Using Organize Imports, CMD+SHIFT+O (OSX) or CTRIL+SHIFT+O (Win) will both remove unused import statements and add any import statements your code needs. With our Main class active in the editor [43], use the Organize Imports key stoke to get rid of that unused 'Shape' import statement [44]. [edit]