016: Effective Java for Android developers : Item 2

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.

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Show Notes

• Effective Java (2nd Edition) - Joshua Bloch

Consider a builder when faced with many constructor parameters

Patterns available for constructing object with parameters:

• Telescoping Constructor Pattern - Provideconstructor 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
• JavaBeans Pattern - Callparameterless 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.
• Builder pattern - winner!
  • 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]

Tip:

• Use IntelliJ to generate your Builders easily

Contact us:

• @fragmentedcast [twitter.com]
• @donnfelker [twitter.com]
• @kaushikgopal [twitter.com]

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