java: most concise way to compare one variable against several others

Question

Often I find myself writing if statements like this...

if (name.equals("fred") || name.equals("bob") || name.equals("jack")){

}

or with primitives...

if (numb==4 || numb==45 || numb=91){

}

Is there a more concise way to do this?

edit: My question is indeed a duplicate. To anyone reading this, I recommmend having a look at the other threads too - they have some good stuff.

`switch`......? [The switch Statement](http://docs.oracle.com/javase/tutorial/java/nutsandbolts/switch.html) — MadProgrammer, Jan 15 '15 at 01:16
@KickButtowski That doesn't make sense. A value cannot be equal to multiple primitives, right? — k_g, Jan 15 '15 at 01:19
@k_g I did not talk about this specific situation, yet I asked in general? — Kick Buttowski, Jan 15 '15 at 01:20
Another duplicate here: http://stackoverflow.com/questions/20952325/a-cleaner-if-statement/20952404#20952404 — Kevin Workman, Jan 15 '15 at 01:30
I don't think this should be a duplicate. yes, regarding strings, it is, but the original poster also asked for other objects and primitives. This isn't a String exclusive post. — EDToaster, Jan 15 '15 at 01:30
If you have a moderately large number of strings, consider using a `Set`. Besides efficiency (since it will look for a hash instead of comparing with every string), it makes it easier to encapsulate the place where your `Set` is created, and possibly put the set data in a place that's more logical in your program. Also makes it easier to customize the data in the `Set` (e.g. if you're looking for a set of user commands, but then want to support users who speak a different language). — ajb, Jan 15 '15 at 01:46

EDToaster · Accepted Answer · 2015-01-21T22:22:25.423

3

You could use switch and case statements:

for example instead of:

if (numb==4 || numb==45 || numb=91){
    //do stuff
}

you could do:

switch(numb){
    case 4:
    case 45:
    case 91:
        //do something regarding the numbers 4 45 and 91
        break;
    default:
        break;
}

If you are big on readability (since it is what this question is concerned about), you could also create line breaks between the boolean checks:

if(name.veryLongMethodHere("fred") ||
   name.veryLongMethodHere("bob") ||
   name.veryLongMethodHere("food")){
    //do more stuff   
}

this is a very good way to organize code if you have very long and complicated methods.

Even better yet, using regex for String objects: if(name.matches("bob|food|fred"){ //do something }

edited Jan 21 '15 at 22:22

answered Jan 15 '15 at 01:17

EDToaster

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1

Doesn't look more concise to me... – August Jan 15 '15 at 01:17
2

If you have 30 choices, it is, and more readable imo. – Kyranstar Jan 15 '15 at 01:18
1

@August I find it a lot more readable and easy to format. – EDToaster Jan 15 '15 at 01:19
what is gonna happen if you have && instead of ||? – Kick Buttowski Jan 15 '15 at 01:19
1

@KickButtowski What number is equal to 4, 45, and 91 all at once? That is a nonsensical situation. – ApproachingDarknessFish Jan 15 '15 at 01:30
@approachingDarknessFish +1 for amazing username XD :P and because it is helpful – EDToaster Jan 15 '15 at 01:47

MadProgrammer · Answer 2 · 2015-01-15T01:30:22.523

2

You could...

Use a switch statement...

switch (name) {
    case "fred":
    case "bob":
    case "jack":
        break;
}

And

switch (numb) {
    case 4:
    case 45:
    case 91:
        break;
}

You could...

Use a Collection of some type...

if (Arrays.asList("fred", "bob", "jack").contains("fred")) {
    // Have match
}

Which is useful if you have dynamic values...

You could also use something like...

if (Arrays.asList("fred", "bob", "jack").containsAll(Arrays.asList("fred", "bob", "jack"))) {
    // Have match
}

If you need to to use && instead of ||...

You could also substitute the long hand String list with a predefined array or List, which could allow you to write a single method...

public <T> boolean matchOR(List<T> want, T have) {

    return want.contains(have);

}

public <T> boolean matchAnd(List<T> want, List<T> have) {

    return want.containsAll(have);

}

Which would allow you to write something like...

if (matchOr(Arrays.asList("fred", "bob", "jack"), name)) {
    //...
}

As an idea...

At some point, context will need to be considered, for example, the above examples allow you to provide a flexible series of conditions, but you might not want to do this and will have to write your if statements as you have been

edited Jan 15 '15 at 01:30

answered Jan 15 '15 at 01:17

MadProgrammer

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how about if you had && instead of ||? – Kick Buttowski Jan 15 '15 at 01:18
Might be interesting to add to your answer that switching on a String is supported since Java 7. – Philippe Aubertin Jan 15 '15 at 01:19
@KickButtowski Then you can't do it, obviously, but that's not what the OP asked. – user207421 Jan 15 '15 at 01:19
@KickButtowski Also, a value can't be `==2` and `==5` simultaneously. Just skip that block. – k_g Jan 15 '15 at 01:19
@k_g good point to address, but I asked that in general – Kick Buttowski Jan 15 '15 at 01:20
@KickButtowski Use a separate case block – MadProgrammer Jan 15 '15 at 01:20
@MadProgrammer could you please be kind and address that inside your post so I can vote u up? – Kick Buttowski Jan 15 '15 at 01:21
3

@KickButtowski Huh? In what case would you have multiple equalities containing the same variable? Can you give a situation?j – k_g Jan 15 '15 at 01:22
:D I dont ask about this specific condition. I am talking about other cases that you need to have multiple && – Kick Buttowski Jan 15 '15 at 01:23
The original poster is asking for a check with multiple possibilities, I don't see the third option as more efficient, because it doesn't shorten the `if` statement if you need to check for more than one thing. EDIT: nevermind XD you edited it. – EDToaster Jan 15 '15 at 01:23
@KickButtowski Take a look at the last example – MadProgrammer Jan 15 '15 at 01:27
@KickButtowski Link me up – MadProgrammer Jan 15 '15 at 01:33

score 2 · Answer 3 · answered Jan 15 '15 at 01:22

The real answer is that you shouldn't always go for more "concise". Go for what's most readable, unless you're experiencing some kind of efficiency problem.

That being said, I'll throw in yet another way to do this:

    if(Arrays.asList("fred", "bob", "jack").contains(name)){

    }

java: most concise way to compare one variable against several others

3 Answers3

You could...

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