J2ME performance optimization tips & tricks
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J2ME performance optimization tips & tricks

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J2ME performance optimization tips & tricks Presentation Transcript

  • 1. Micro Java
    Performance Tuning & optimization
  • 2. Device limitations
    Runtime memory
    Processor speed
    Slow network bandwidth
    Screen resolutions
    Restricted storage
  • 3. Performance Tuning
    Tips & tricks
    Good & ugly practice
    Performance tuning
    Tools usages
    Effective usages of design patterns
  • 4. Tips & tricks
    Use “Out of memory Exception” handlers on each initialization
    Avoid inner classes: make the main class implement the required Listener interfaces and handle the call-backs there.
    Collapse inheritance hierarchy, even it means duplicating code
    Shorten all name qualifiers (package, class, method, variable names)
    Minimize the number of array
    Reduce try-catch blocks to bare minimum
    Use lower versions of JDK while packaging JAR files, JAR File size created using JDK 1.3 is 5% to 20% lesser than those created with JDK1.4.
    Scope of variables/classes/methods can impact performance
    Eliminate unnecessary type casts
  • 5. Tips & tricks-II
    Compound operators are faster, because fewer byte codes are generated
    Define methods that accept reusable objects to be filled in with data, rather than methods that return objects holding that data
    Inline methods where ever it is possible.
    Use private and static methods and final classes to encourage in lining by the compiler.
    keep synchronized method out of loop, it increases the overhead
    Avoid synchronization where ever its possible
    Minimize using the methods use native call
    Be specific for throwing and handling exceptions
  • 6. Creating objects in loop
    Imposes double penalty in terms of performance
    Each iteration in loop pushes the runtime system closer to garbage collector
    Restructure code instead creating new processor each time
  • 7. Good practice
    Bad practice
    Object[] inputs = new Object[0];
    int[] results = new int[0];
    int length = inputs.length;
    Processor p = new Processor();
    for (int i = 0; i < length; i++) {
    p.setInput(inputs[i]);
    results[i] = p.calculateResult();
    }
    Object[] inputs = new Object[0];
    int[] results = new int[0];
    int length = inputs.length;
    for (int i = 0; i < length; i++) {
    Processor p = new Processor(inputs[i]);
    results[i] = p.calculateResult();
    }
  • 8. String & Stringbuffer
    String is only the data type which can overload + operator in java
    Each time you connate a string it inters creates a string buffer and string buffer creates performs over byte array
    String buffer in efficient then string, but not always
  • 9. Performance Tuning
  • 10. BE clean
    Release resource
    Free the used internal data structures
    Set array references to null after usage
    Close network connections in finally block
  • 11. Optimizing User interface
    Need to be simple, fast, informative and responsive
    Progress indicator while network / other processing
    Usage of low resolution images maintaining the minimal quality
    Use double buffering technique for images where ever it applies
    Use client caching
    Use paint or partial paint the screen where ever necessary
  • 12. Optimizing Application deployment
    Usage of obfuscator packages
    Usage of low resolution images maintaining the minimal quality
    Include only the classes you need
    Use public variables in your classes, rather than using assessors. It is practically bad practice but reduces app size
    Use protected methods
  • 13. Use of obfuscator
    Reduces .jar size
    Byte code obfuscator makes the code difficult to decompile
    Side effect- descriptive method and variable names gets converted to small machine generated names
    Obfuscators are
    Retro guard
    Pro guard
    IBM JAX
  • 14. Benchmarking
    J2SE has many tools for benchmarking
    In ME we use “java.lang.runtime” class methods for memory test
    freeMemory()
    totalMemory()
  • 15. Knowing the runtime free memory
    Runtime runtime = Runtime.getRuntime();
    long before, after;
    System.gc();
    before = runtime.freeMemory();
    Object newObject = new String();
    after = runtime.freeMemory();
    long size = before - after;
  • 16. Knowing execution time for a method
    Use System.currentTimeMiles()
    long start, finish;
    start = System.currentTimeMillis();
    someMethod();
    finish = System.currentTimeMillis();
    long duration = finish - start;
  • 17. MIDP Performance monitor Tools
    Collects the statistics of application
    Tools used in J2ME wireless tool kit are:
    Profiler
    Memory monitor
    Network monitor
  • 18. Midlet Profiler
    Collects the statistics of application
    To monitor the method call and time to execute a method
    Includes MIDP reference implementation classes
  • 19. Call Graph
  • 20. Memory monitor
    Object Graph
  • 21. Network Monitor
    Request Response
  • 22. Conclusion
    Only optimize code if you need to and where it counts
    Always study your code and try to improve the algorithms before using low-level techniques
    Use setClip() where possible to minimize the drawing area
    Keep as much stuff as possible out of loops
    Pre-calculate and cache like crazy
    Use static final methods where possible and avoid the synchronized modifier
    Pass as few parameters as possible into frequently-called methods
    Try to compare to zero instead of any other number
    Local variables are faster than instance variables