062: Effective Java for Android Developers – Item #12: Consider Implementing Comparable

In this mini-Fragment episode, Donn talks about Item #12 of the Effective Java series – Consider Implementing Comparable. You’ll learn about how you can use the Comparable interface to give your code the extra sorting boost it needs. Work with Arrays.sort(), Collections utilities and even sorted data structures. Donn breaks down what it takes to implement the compareTo method of the Comparable interface.

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058: Effective Java for Android Developers – Item #11: Override clone Judiciously

In this mini-Fragment, Donn talks about Item #11 of the Effective Java series – Override clone Judiciously. You’ll learn about the extralinguistic behavior of clone and the Cloneable interface. Clone and Cloneable are very special, and this episode helps explain the nuances.

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044 – Effective Java for Android Developers – Item #10

In this mini-Fragment, Donn talks about Item #10 of the Effective Java series – Always Override toString. You’ll learn why it’s important for your own sanity, future developers, and overall developer happiness.

This episode is sponsored by Hired.com.

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034: Effective Java for Android Developers – Item #9

In this mini Fragment, we introduce Joshua’s ninth Item. After the last somewhat mind boggling item, this is a much welcomed simple, practical yet important one: Always override hashCode when you override equals.

Donn goes into the importance of implementing hashCode and why it’s so important to override it for maintaining harmony with the equals method. Also 42 and the answer to life ? He then goes into some tips on implementing a good hashCode and a standard recipe for the same.

Go forth and override them hashCodes!

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This episode is brought to you by Rollbar. Go to rollbar.com/fragmented to get their Bootstrap plan for free for 90 days. Stay tuned for more items from our “Effective Java for Android developers” Fragment series.

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031: Effective Java for Android Developers – Item #8

In this mini Fragment, we introduce Joshua’s eighth Item. This one is a doozy, probably one of the longest items in the group of the effective Java series, but most definitely quite important.

This episode is brought to you by Rollbar. Go to rollbar.com/fragmented to get their Bootstrap plan for free for 90 days.

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

Show Notes

Obey the general contract when overriding equals

When to not override equals:

  • Each instance of the class is inherently unique.
  • You don’t care whether the class provides a “logical equality” test.
  • A superclass has already overridden equals, and the superclass behavior is appropriate for this class.

The equals method implement an equivalence relation which states it must be:

  • Reflexive
  • Symmetric
  • Transitive
  • Consistent
  • For any non-null reference x, x.equals(null) must return false.

A recipe for a high-quality equals method is as such:

  • Use the == operator to check for references to this object.
  • Use the instanceof operator to check if the argument has the correct type 
  • Cast to the correct type.
  • Check all field types and corresponding field types.
  • Finally, when done, ask yourself – is this method symmetric, transitive and consistent?

Caveats

  • Always override hashcode when you override equals
  • Don’t be too clever!
  • Don’t substitute another type for Object in the equals declaration.

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