What is better: multiple "if" statements or one "if" with multiple conditions?

java optimization if-statement multiple-conditions
3rgo picture 3rgo · Mar 10, 2011 · Viewed 79.3k times · Source

For my work I have to develop a small Java application that parses very large XML files (~300k lines) to select very specific data (using Pattern), so I'm trying to optimize it a little. I was wondering what was better between these 2 snippets:

if (boolean_condition && matcher.find(string)) {
    ...
}

OR

if (boolean_condition) {
    if (matcher.find(string)) {
        ...
    }
}

Other details:

  • These if statements are executed on each iteration inside a loop (~20k iterations)
  • The boolean_condition is a boolean calculated on each iteration using an external function
  • If the boolean is set to false, I don't need to test the regular expression for matches

Thanks for your help.

Answer

adarshr picture adarshr · Mar 10, 2011

One golden rule I follow is to "Avoid Nesting" as much as I can. But if it is at the cost of making my single if condition too complex, I don't mind nesting it out.

Besides you're using the short-circuit && operator. So if the boolean is false, it won't even try matching!

So,

if (boolean_condition && matcher.find(string)) {
    ...
}

is the way to go!

Related questions

Why is processing a sorted array faster than processing an unsorted array?

Here is a piece of C++ code that shows some very peculiar behavior. For some strange reason, sorting the data miraculously makes the code almost six times faster: #include <algorithm> #include <ctime> #include <iostream> …

Read More
Fastest way to determine if an integer's square root is an integer

I'm looking for the fastest way to determine if a long value is a perfect square (i.e. its square root is another integer): I've done it the easy way, by using the built-in Math.sqrt() function, but I'm wondering …

Read More
Most efficient way to increment a Map value in Java

I hope this question is not considered too basic for this forum, but we'll see. I'm wondering how to refactor some code for better performance that is getting run a bunch of times. Say I'm creating a word frequency list, …

Read More