–to change default from src and bin to something else, like “classes”,
window -> preferences -> java -> build path
–to change per-project setting
project -> properties -> java build path -> source -> go to page bottom.
You can set “Default output folder” to “myproject1/classes” even though there’s no physical directory named “myproject1”. Instead, the ../classes/ directory will show up in the project’s root directory — confusing.
Similar confusion arises when you see an explorer-style directory tree with “myproject1” as the root (no such directory) and real directories as branches.