Simplifying/optimizing massive if...else if...else statement(s)

Question

Okay so essentially, I have some code that uses the contains() method to detect the presence of specific characters in two strings. For extra context, this question is a good resource as to what kind of problem I'm having (and the third solution is also something I've looked into for this). Regardless, here is some of my code:

// code up here basically just concatenates different
// characters to Strings: stringX and stringY

if (stringX.contains("!\"#")) {
} else if (stringX.contains("$%&")) {
} else if (stringX.contains("\'()")) {
} else if (stringX.contains("!$\'")) {
} else if (stringX.contains("\"%(")) {
// literally 70+ more else-if statements
}

if (stringY.contains("!\"#")) {
} else if (stringY.contains("$%&")) {
} else if (stringY.contains("\'()")) {
} else if (stringY.contains("!$\'")) {
} else if (stringY.contains("\"%(")) {
// literally 70+ more else-if statements, all of which are
// exactly the same as those working with stringX
}

I'm still pretty new to Java programming, so I'm not sure how I should go about this. Maybe it is a non-issue? Also, if I can remedy this without using RegEx, that would be preferable; I am not very knowledgeable in it at this point it time. But if the only rational solution would be to utilize it, I will obviously do so.

Edit: The code within all of these else-if statements will not be very different from each other at all; basically just a System.out.println() with some information about what characters stringX/stringY contains.

More generally, the go-to answer here is _Replace Conditional with Polymorphism_. Specifically, it looks like you have a `Map>` and something like `map.entrySet().stream().filter(e -> stringX.contains(e.getKey())).findFirst().ifPresent(e -> e.getValue().accept(stringX));`. — chrylis -cautiouslyoptimistic-, Aug 03 '20 at 03:47
Is this precedence required? I.e., it will only search for `$%&` when `!"#` has not been found. — Holger, Aug 06 '20 at 12:57

Hiep Le · Answer 1 · 2020-08-03T03:56:38.283

3

can simply by make a list of your case. then using java 8 stream filter

List<String> pattems = Arrays.asList("!\"#", "$%&", ...);
Optional<String> matched = pattems.stream().filter(p -> stringX.contains(p));
if(matched.isPresent()) {
   System.console().printf(matched.get())
}

java stream could make your peformance slower but not too much

edited Aug 03 '20 at 03:56

answered Aug 03 '20 at 03:48

Hiep Le

323
2
13

Elan Hamburger · Accepted Answer · 2020-08-03T03:59:47.533

3

Writing the same code more than once should immediately set off alarm bells in your head to move that code into a function so it can be reused.

As for simplifying the expression, the best approach is probably storing the patterns you're looking for as an array and iterating over the array with your condition.

private static final String[] patterns = new String[] {"!\"#", "$%&", "\'()", "!$\'", "\"%(", ...};

private static void findPatterns(String input) {
    for (String pattern : patterns) {
        if (input.contains(pattern) {
            System.out.println("Found pattern: " + pattern);
        }
    }
}

// Elsewhere...
findPatterns(stringX);
findPatterns(stringY);

This pattern is especially common in functional and functional-style languages. Java 8 streams are a good example, so you could equivalently do

List<String> patterns = Arrays.asList("!\"#", "$%&", "\'()", "!$\'", "\"%(", ...);
patterns.stream()
    .filter(pattern -> stringX.contains(pattern))
    .forEach(pattern -> System.out.println("Found pattern: " + pattern));

edited Aug 03 '20 at 03:59

answered Aug 03 '20 at 03:53

Elan Hamburger

2,137
10
14

1

Given that the function is not _exactly_ the same, a map is probably going to be the structure of choice. – chrylis -cautiouslyoptimistic- Aug 03 '20 at 04:36
@Elan Hamburger | Thank you, Mx. Hamburger. I think for my simple project, the former option will be suitable, not that any of the other answers are wrong or worse than this one. Just one question: if I made `patterns` a two-dimensional array, could I reference specific character combinations with `for (String pattern : patterns[a][b])`? According to my Java notebook, I can possibly do this with multiple `for` loops, but not a single `for-each` loop. It won't make too much of a difference for me, so I'm really just curious. – ajent Aug 03 '20 at 21:33
Nevermind, don't bother with that; [this answer](https://stackoverflow.com/a/12760783/13926001) was a good resource. Thanks again! – ajent Aug 03 '20 at 22:09

Simplifying/optimizing massive if...else if...else statement(s)

2 Answers2