FAQ Where do my class files disappear to?
If you use the context menu on a project to inspect the projects properties, the Java Build Path page will have a field for the Default output folder. The initial value is the bin directory directly under your project. Similarly, the Source tab provides access to the location of your source input folder(s).
The Java perspective filters out the output folder from the Package Explorer. If you like, you can use the Navigator view to browse the output folder.