On a Windows 7 PC, these files were getting enormous, and causing problems with the size of my roaming profile. Metalink Note ID 1943500.1 gives a solution for SQL Developer, which also seems to work for JDeveloper.
The all-resources.dat file can be found in:
The fix is as follows…
Add the following text to the sqldeveloper.conf file (in the sqldeveloper\bin directory):
For JDeveloper, add the same line of text to the jdev.conf file (in the jdev\bin directory).
The all-resources.dat files can then be permanently deleted (Shift-Delete) to free up a considerable amount of roaming profile space.