0

I produced code

for(String buff : Arrays.asList(
        FORMULA_PATTERN.matcher(s).group().split("\n")
        )

And I started wondering where performance lies with not creating an explicit local container for method returns. (Also, I'm not sure that this works, I'm just prototyping some stuff while waiting for full specs)

Related to Java coding style, local variables vs repeated method calls but I'm curious of the actuality of it.

for the coding pattern (not the specific case, just examples)

Integer.parseInt(buff.substring(buff.length()-1));

Is there any gain/loss over

int x = buff.length() -1;
Integer.parseInt(buff.substring(x);

Or, for the more general case of the language, avoiding primitives

Integer x = buff.length() -1;
Integer.parseInt(buff.substring(x);

This may differ for collections, but my curiosity is the cost associated with Java's pass by value having a cost to instantiate an object to be returned.

Not really concerned with readability, just wondering if, when, and how one method would outperform the other.

Improve this question
5
  • I doubt that there is any difference between Integer.parseInt(buff.substring(buff.length()-1)); and int x = buff.length() -1; Integer.parseInt(buff.substring(x);. int x in the latter is probably optimized away anyway. Commented Jul 9, 2015 at 18:13
  • YMMV. Test it with your compiler and VM if it's important. It's probably not important. There might be some small constant difference, but no big win. Boxing a primitive int into an Integer and then unboxing again is definitely not an improvement. In general, prefer readability over premature optimization. Commented Jul 9, 2015 at 18:19
  • Editted to clarify. I wasn't looking at those examples as SPECIFIC cases, just the difference of storing the return value of something as a box-unbox pair. Commented Jul 9, 2015 at 18:27
  • 1
    I'm having trouble following what you're asking here. Your initial example seems to include a superfluous ArrayList instantiation, the for loop can iterate right over the array. As far as use of intermediate local vars for clarity, that sort of thing has either no practical performance implication and/or is optimized away. Feel free to use them. Commented Jul 9, 2015 at 18:36
  • Probably just bad code on my part, prototyping through a bunch of solutions, it's probably remnants of the last solution I forgot to trim. I was doing character handling before moving to regex and I was having to convert between char[] and Character[]. Commented Jul 9, 2015 at 18:39
Related questions
4
In Java, is it more expensive to create an object, or get the objects value?
1
Setting a Field vs. Creating a new Object
1
any difference in efficiency between accessing an object or creating a referenced object?
Load 7 more related questions Show fewer related questions

0

Reset to default

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.