Eclipse: how to hide custom files in Project Explorer

Here's how to do it on Eclipse Indigo/Luna/Neon (as of 2018-05-22):

• Open the "project properties"
  • pull down menu --> Project --> Properties
  • A new dialog window named "Properties" will appear
• Create a "Resource Filter"
  • Select Resource --> Resource Filters -> Add Filter...
  • A new dialog window named "Add Resource Filter for project" will appear
  • In the new dialog select the following
    • Filter Type: Exclude All
    • Applies to: Files
    • Make sure to click the checkbox for "All children (recusive)"
    • File and Folder Attributes
      • select: Name
      • select: Matches
      • fill in: *.ooj
    • Click OK
    • Dialog closes
• Apply the new filter
  • Click Apply
  • You should see a change in your "Navigator" View
• Close the "Project Properties"
  • Click OK
• Done

You can define a filter for that. Open the view menu in the Package Explorer and then choose "Filters..." Here you can define a pattern to hide files.