I have to run my Android app on another platform, such as Nokia Symbian or Java. Is there any solution for such a conversion?
No. The APIs are far too intertwined with the Android OS. Symbian or Java will not offer the same set of classes for display, OS integration, apps, accelerometor/sensors, and almost anything else.
You can, however, refactor OS-agnostic code into new classes and reuse those for Java platforms.