Checking if an array contains one integer value

Question

Don't want to use loops. I tried the below code but it doesn't work for primitive types.

if ( Arrays.asList( myMatrix ).contains( -1 ) )
{
    // do something
}

What shall be done here?

You need a loop to do this, and the example you posted demonstrates lazy, inefficient coding — ControlAltDel
– ControlAltDel, Commented Dec 6, 2015 at 1:09
@ControlAltDel: I agree with that, but in Ezazel's defense, (1) a lot of people advocate using stuff like the Streams API these days , (2) there really should be a contains method on java.util.Arrays, and (3) that some stuff does not work with int, but works with Integer is a bit lame. — Thilo
– Thilo, Commented Dec 6, 2015 at 1:18

Pshemo · Accepted Answer · 2015-12-06 01:26:22Z

3

You can't avoid iteration in your code since we need some way to test all elements in your array (at least until we will find the one we are looking for). But to make your life easier create some additional utility method like (name could be probably better/more descriptive) public static boolean contains(int[] array, int element) which will handle iteration for us. Then simply use it like if(contains(matrix, -1)).

In Java 8 you could use IntStream which handles int[] myMatrix array correctly (like Array.asList handles Integer[] myMatrix).

So as condition you could use something like:

IntStream.of(myMatrix).anyMatch(i -> i == -1)

edited Dec 6, 2015 at 1:26

answered Dec 6, 2015 at 1:18

Pshemo

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2 Comments

Thilo Over a year ago

I upvoted, because that is what the question asked for. But I would not do that in this case. Cannot be faster, arguably harder to read.

Pshemo Over a year ago

@Thilo Agreed. I only posted it as example of how code can look like. But I am surprised that Arrays doesn't have method which handles this task already. EDIT: based on your answer I see we agree on that.

Thilo · Accepted Answer · 2015-12-06 01:26:51Z

3

Java should really have a method contains on java.util.Arrays.

Commons Lang has it, for example.

So I would either find it in the libraries I already use, or make a static helper method myself (with a simple loop inside).

answered Dec 6, 2015 at 1:26

Thilo

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Comments

Hovercraft Full Of Eels · Accepted Answer · 2015-12-06 01:12:12Z

2

"I don't want to use loops" -- you can't always get what you want, and in fact in this situation, use a loop.

answered Dec 6, 2015 at 1:12

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Hovercraft Full Of Eels

8 Comments

Thilo Over a year ago

You could hide that loop behind contains, but there is still a loop in there.

Thilo Over a year ago

You cannot directly use contains on an array of primitives. You have to jump through some hoops (and potential inefficiencies). But that's more of a failing of Java than the programmer's in my book.

Hovercraft Full Of Eels Over a year ago

@Thilo: thanks. And 1+ to Pshemo's answer, although if I had the energy, I'd look through the source code generated by it.

Hovercraft Full Of Eels Over a year ago

@Ashiquzzaman: to be honest, I didn't much like the question, or my answer.

Thilo Over a year ago

I don't like my answer either. Or the other one. Even though all three are correct. Sad situation all around. This kind of stuff makes people roll their eyes at Java.

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