Steps:

1. Create a Java project
2. Create a new java package - newpackage
3. Create a new java class NewClass in newpackage
4. Create a new java class NewClass1 in newpackage
5. Add a statement new NewClass(); in NewClass1 constructor.
6. Create a new java package - newpackage.newsubpackage
7. Copy and paste newpackage.NewClass1 to newpackage.newsubpackage
8. Open newpackage.newsubpackage.NewClass1.
9. See a red sqigly underline under statement new NewClass();

This happens because the import newpackage; statement is missing in 
newpackage.newsubpackage.NewClass1.

Woraround is to invoke Fix Imports action.