In our third Fragment installment, we introduce Josh’s second Item: Consider a builder when faced with many constructor parameters.
Stay tuned for more items from our “Effective Java for Android developers” Fragment series.
Consider a builder when faced with many constructor parameters
Telescoping Constructor Pattern
- Provide constructor with only required parameters, another with a single optional param, a third with 2 optional params… and so on.
- Advantage: Works well for small number of parameters
- Disadvantage: Does NOT scale well
- Call parameterless constructor to create the object; then call setter methods to set required parameter and each optional param of interest.
- Advantage: Scales well, easy (but wordy) to read resulting code
- Disadvantage: Allows inconsistency (if all required params not called); impossible to make classes immutable if using this pattern.
- Advantage: Simulates named optional parameters; allows immutable objects to be constructed; flexible
- Disadvantage: more ceremony to actually construct the Builder Class and finally use.
Example usage from Android source:
- AlertDialog Builder [androidxref.com]