Switch case statement error: case expressions must be constant expression
To fix the "case expressions must be constant expression" issue, use final declarations or literal values in your switch case labels. Java demands that case labels be compile-time constants. Demonstrating a correct usage:
Alternatively, if-else structures can come in handy if you can't deal with the whole constant thing.
Solution for non-final constants
When working with Android library projects or R-class in Android, it's almost inevitable to encounter errors related to non-final constants. These issues are often related to constraints by Android environment, like the post ADT 14 changes.
For such scenarios, you are better off replacing switch case with if-else statements. Button click events, for instance, should preferably use if-else due to these changes.
Good news is that platforms like Android Studio and Eclipse bring you handy shortcuts — Alt+Enter and Ctrl+1 respectively — to speed up your switch to if-else conversion.
Be sure to check your constants and project settings, especially after making changes to your project or updating your build tools. If you've plunged into using the Android Gradle Plugin version 8.0.0, take note the R-class has experienced some lifestyle changes. A quick tweak like adding android.nonFinalResIds=false to your gradle.properties file could set things straight.
Tips and optimizations in real-world coding
Performance considerations
Many programmers often frown upon if-else thinking it's less efficient compared to switch case. But thanks to modern JVM techs like branch prediction and JIT (Just-In-Time) compilation, the performance gap is virtually non-existent, especially in event-driven setups like Android.
Adapting to new tool versions
Whenever you breathe a new version of tools like Android Gradle Plugin, stay aware of changes. Kicking off new projects with version 8.0.0 brings changes to R-classes, essentially altering the behaviour of auto-generated resource IDs.
Effective control structures
For handling complex conditional logic, the traditional switch case might not cut it. Give Strategy or Command design patterns a shot. These allow you to encapsulate the logic in objects, granting you more flexibility and testability than being limited to a rigid switch case statement.
Best practices to follow
- Always assign your constants using the
public static final intsyntax where possible. This helps to maintain efficiency. - If not required, uncheck the 'Is Library' option in project properties to avoid case expression errors.
- Utilize enums for code readability and maintainability. Plus, they work well with switch statements.
Was this article helpful?