How to check multiple variables at once?

Question

Is it possible to write a block of code to check all, or all objects/variables of a certain type for a certain characteristic? (Without creating an if statement for each)
Then set it to something if true or false.

Like if you had 3 variables and...

 if(a=0||b=0||c=0){
//set any variable equal to zero to 4
}

preform the action described in the comment

Or, complex example, 4 arraylists of type integer:

List<Integer> even = new ArrayList<Integer>(), //positive even ints
odd = new ArrayList<Integer>(), //positive odd ints
negaodd = new ArrayList<Integer>() //negative even ints
negaeven = new ArrayList<Integer>(); //negative odd ints

Then something like:

if("AnyArray".isEmpty()){
whatever-array-is-being-tested/tried = null;
}

So that if any of the arrays ended up being empty, then instead of [], they would return "null".

Use an array or a list and loop over its elements. – Sotirios Delimanolis Mar 20 '13 at 23:59 — Sotirios Delimanolis, Mar 20 '13 at 23:59

score 3 · Accepted Answer · edited May 23 '17 at 10:24

3

Hmm, if you wanted to do something more interesting then just iteration over a collection, it does look very functional like applying a filter then map. Try out lambdaj or google collections (see here for a nice post http://codemunchies.com/2009/11/functional-java-filtering-and-ordering-with-google-collections-part-3/). Here is an example using lambdaj from https://code.google.com/p/lambdaj/wiki/LambdajFeatures.

List<Integer> oddNumbers = filter(odd, asList(1, 2, 3, 4, 5));

See here for more potential ideas: What is the best way to filter a Java Collection?

Disclaimer Sometimes going overboard with this sort of thing (when a simple loop would suffice) obfuscates the code more than anything else, so be wary.

edited May 23 '17 at 10:24

Community

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answered Mar 21 '13 at 00:01

Anil Vaitla

2,958
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1

I like the disclaimer... and hope it's taken to heart. – jahroy Mar 21 '13 at 00:16
Link provided by you is not working – Subodh Joshi Jul 23 '15 at 08:55

jahroy · Answer 2 · 2013-03-21T00:34:02.267

You could use an array or a list along with a helper method to achieve either.

int[] intArray = { a, b, c };
setZeroes(intArray);

public void setZeroes(int[] a) {
    for (int i = 0; i < a.length; i++) {
        a[i] = (a[i] == 0) ? a[i] : 4;
    }
}

Note that this won't set a, b, or c to 0, but rather the elements in the array.

But... maybe they should just be elements of an array (or List) anyways. That's my hunch.

You could do the same thing with a List of Lists.

List<List<Integer>> listOfLists = new ArrayList<List<Integer>>();
listOfLists.add(listA);
listOfLists.add(listB);
listOfLists.add(listB);
setListsToNull(listArray);

public void setListsToNull(List<List<Integer>> a) {
    for (int i = 0; i < a.length; i++) {
        List<Integer> thisList = a.get(i);
        a.set(i, thisList.isEmpty() ? null : thisList);
    }
}

I would typically use an if statement in stead of the ? operator, but you wanted no ifs....

You could easily make both methods generic (you'd have to use objects for the first example), but we'll leave that up to you....

How to check multiple variables at once?

2 Answers2