For some, developing for the Android platform might provide their first experience of working with a complex, modern Java API. This may test your knowledge of the Java programming language, especially with regard to features such as generics. The Android APIs make use of generics throughout and so you will have to know how to create and handle generic classes.

1. Software Engineering Large Practical
Common Java problems when coding for
Android and advice for dealing with them
Stephen Gilmore
School of Informatics, University of Edinburgh
October 24th, 2012
Stephen Gilmore Software Engineering Large Practical

2. Java problems
For some, developing for the Android platform might provide their
first experience of working with a complex, modern Java API. This
may test your knowledge of the Java programming language,
especially with regard to features such as generics. The Android
APIs make use of generics throughout and so you will have to
know how to create and handle generic classes.
Stephen Gilmore Software Engineering Large Practical

3. Raw types
Raw types are a backwards compatibility feature which allowed
new generic Java code to use old non-generic libraries and to allow
non-generic Java code to continue to compile and work on modern
Java versions. Raw types are not needed when working with the
Android API and your project should not contain them.
Stephen Gilmore Software Engineering Large Practical

4. Common Java problems: raw types, 8 warnings
Stephen Gilmore Software Engineering Large Practical

5. Quick fix: a bad suggestion
Stephen Gilmore Software Engineering Large Practical

6. Check the constructor documentation
Stephen Gilmore Software Engineering Large Practical

7. Check the class documentation
Stephen Gilmore Software Engineering Large Practical

8. What type of array are we adapting?
Stephen Gilmore Software Engineering Large Practical

9. Type parameter added, 6 warnings
Stephen Gilmore Software Engineering Large Practical

10. Raw type parameters
Raw types need special treatment in method headers when
instances of generic classes are being passed as parameters to
methods. A special syntax is used to specify when we do not know
the type of the parameter to the generic class.
Stephen Gilmore Software Engineering Large Practical

11. Raw type in method header, 5 warnings
Stephen Gilmore Software Engineering Large Practical

12. Consult the Java documentation
Stephen Gilmore Software Engineering Large Practical

13. Adapter doesn’t work here
Stephen Gilmore Software Engineering Large Practical

14. Adapter is an interface
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15. T is not a class
Stephen Gilmore Software Engineering Large Practical

16. Object: the goto class
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17. T extends Adapter doesn’t work
Stephen Gilmore Software Engineering Large Practical

18. “?” — the wild card parameter, 3 warnings
Stephen Gilmore Software Engineering Large Practical

19. “Quick fix” would have worked here
Stephen Gilmore Software Engineering Large Practical

20. Same result
Stephen Gilmore Software Engineering Large Practical

21. Working with the Java compiler
The Java compiler used Eclipse allows you to tune the level of
checking which your program receives during compilation. This
checking (“static analysis”) evaluates the correctness of your
program without executing it.
The default settings do not apply particularly strict checking. We
recommend tightening the default settings to detect errors in your
Java code which you may otherwise miss.
Stephen Gilmore Software Engineering Large Practical

22. Setting Java compiler preferences
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23. Changing defaults
Stephen Gilmore Software Engineering Large Practical

24. Potential programming problems
Stephen Gilmore Software Engineering Large Practical

25. Tighter checking
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26. Bug found
Stephen Gilmore Software Engineering Large Practical

27. Remembering and forgetting while developing
Leaving an empty block is a classic “I must remember to do that
later” error. By turning on stricter checking with the static
analysis tools in the Java compiler we get automatic reminders in
the form of Java problems. These will persist in our project until
we do go back and write the remaining code block.
Stephen Gilmore Software Engineering Large Practical

28. Logging
As we have seen, the Android emulator occupies all of the screen
real estate of our virtual device, in order to allow us to test apps as
they will be used in practice. If we want to log informational
messages for our own purposes then we should use the Android
logging API.
Stephen Gilmore Software Engineering Large Practical

29. Don’t forget to add logging . . .
ng
Stephen Gilmore Software Engineering Large Practical