Fragmented - Android Developer Podcast

018: Effective Java for Android developers : Item 3

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In this mini Fragment, we introduce Joshua's third Item: Enforce the Singleton property with a private constructor or an enum type.

Stay tuned for more items from our "Effective Java for Android developers" Fragment series.

Show Notes
  • Effective Java (2nd Edition) - Joshua Bloch

    • Enforce the Singleton property with a private constructor or an enum type

    Approaches

    1. Create a public static final INSTANCE variable and privatize constructor
    2. Same as 1 but privatize variable and expose access with provide factory method getInstance
    3. Single element Enums

      4. Considerations

      • First two approaches are open to Serialization attacks (deserializing creates new instance)
      • To protect from those declare the fields transient + provide readResolve method
      • Enums are concise, provide free serialization and ironclad Singleton guarantees and are functionally equivalent to first approach

        • Supplemental reading (for the diligent ones that follow shownotes)

        • Dianne Hackborn regretting exposing the base Application class
        • DH again saying Application is a Singleton with crappier semantics
        • Elvis sightings
          • Contact us:
          • @fragmentedcast [twitter.com]
          • @donnfelker [twitter.com]
          • @kaushikgopal [twitter.com]
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