Category: Fragments

In this mini Fragment, we introduce Joshua’s seventh Item and a momentous end to the first chapter: Avoid finalizers

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

Avoid finalizers

• If you don’t know what they are, ignorance is bliss. If you know what they are, avoid them!
• Finalizers in Java != destructors in C++ (C++ counterparts to constructors).
• In C++ destructors
  • you reclaim resources here (Java has GC)
  • you also reclaim non-memory resources (use the try-finally block in Java)
• (unpredicatable amt of time between object becoming unreachable and finalizer being executed) Never do anything time critical in finalizer!
  • System.gc + System.runFinalization increase chances – no guarantee
  • System.runFinalizersOnExit + Runtime.runFinalizersOnExit are the ones that do – but they are fatally flawed
• Java 7 has try with resources, which is also interesting and auto-closeables. [Android] devs can only dream of these.
• If an uncaught exception is thrown in a finalizer, it is ignored, and the finalization abruptly terminates.
• Severe performance penalty for using finalizers – (one e.g.) time to create and destroy simple object goes from 5.6ns -> 2400ns
• Only valid use: as a safety net or to terminate noncritical native resources.
• [Android] you’re probably better off using Android’s lifecycle methods.

Contact

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

Joshua’s sixth Item: Eliminate obsolete object references, in a distinctively croaky voice.

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

Eliminate obsolete object references

Supplemental reading (for the diligent ones that follow shownotes)

• Do click listeners leak memory? [stackoverflow.com]
• Square’s LeakCanary
• How to leak a context – Handlers and inner classes [androiddesignpatterns.com]
• Avoiding Memory leaks [android-developers.blogspot.com]

Contact

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

In this mini Fragment, we introduce Joshua’s fifth Item: Avoid creating unnecessary objects.

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

Avoid creating unnecessary objects

• Google says – Avoiding creating unnecessary objects too!
• Episode 10 with Michael Bailey – String optimization

Snippet to demonstrate AutoBoxing problems

// sum of all positive values
Long sum = 0L;
for (long i=0; i< Integer.MAX_VALUE; i++) {
  sum+=i;
}

Contact

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

Singer and Android developer Donn Felker explores Joshua Bloch’s fourth Item: Enforce noninstantiability with a private constructor.

Stay tuned, cause we got more of these quick ones coming.

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Show Notes:

• Effective Java (2nd Edition) – Joshua Bloch

Enforce noninstantiability with a private constructor.

Examples where you don’t want class to be instantiated

1. class that groups static methods and static fields (Util like classes think java.lang.Math/java.util.Arrays)
2. class that groups static methods (including factory methods) for objects implementing specific interfaces (think java.util.Collections)
3. class that group methods on a final class (vs. extending the class)

Considerations

• Makes no sense to instantiate such “Util” classes
• Private constructors prevent instantiation
• Important side effect: prevents subclassing

Contact us:

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