micro-optimization

Possible Duplicate: Does use of final keyword in Java improve the performance? The final modifier has different consequences in java depending on what you apply it to. What I'm wondering is if additionally it might help the compiler create more efficient bytecode. I suppose the question goes deep into how the JVM work and might be JVM specific. So, in your expertise, do any of the following help the compiler, or do you only use them for the normal java reasons? Final classes Final methods Final fields Final method arguments Thanks! EDIT: Thanks for all your answers! Please note that, as

I wrote two methods to check there performance public class Test1 { private String value; public void notNull(){ if( value != null) { //do something } } public void nullNot(){ if( null != value) { //do something } } } and checked it's byte code after compiling public void notNull(); Code: Stack=1, Locals=1, Args_size=1 0: aload_0 1: getfield #2; //Field value:Ljava/lang/String; 4: ifnull 7 7: return LineNumberTable: line 6: 0 line 9: 7 StackMapTable: number_of_entries = 1 frame_type = 7 /* same */ public void nullNot(); Code: Stack=2, Locals=1, Args_size=1 0: aconst_null 1: aload_0 2: getfield

Are there any considerations that should be taken into account when designing a new table with regards to the order in which columns should be declared? I tend to put the primary key first, followed by any foreign keys (usually surrogate key integers), followed by other columns, but a discussion with a colleague had us wondering whether SQL Server will pad our data, possibly to make it faster. Will SQL Server try and align our data on disk (with padding) to a specific byte alignment boundary for performance reasons (the way a C++ compiler would align a struct under default conditions) or will

a) for(int i = 100000; i > 0; i--) {} b) for(int i = 1; i < 100001; i++) {} The answer is there on this website (question 3). I just can't figure out why? From website: 3. a When you get down to the lowest level (machine code but I'll use assembly since it maps one-to-one mostly), the difference between an empty loop decrementing to 0 and one incrementing to 50 (for example) is often along the lines of: ld a,50 ld a,0 loop: dec a loop: inc a jnz loop cmp a,50 jnz loop That's because the zero flag in most sane CPUs is set by the decrement instruction when you reach zero. The same can't usually

What is the fastest way to strip all non-printable characters from a String in Java? So far I've tried and measured on 138-byte, 131-character String: String's replaceAll() - slowest method 517009 results / sec Precompile a Pattern, then use Matcher's replaceAll() 637836 results / sec Use StringBuffer, get codepoints using codepointAt() one-by-one and append to StringBuffer 711946 results / sec Use StringBuffer, get chars using charAt() one-by-one and append to StringBuffer 1052964 results / sec Preallocate a char[] buffer, get chars using charAt() one-by-one and fill this buffer, then convert