I'm looking for a contains like method for iterable

Question

I have an Iterable and I need to check about a specific string inside the iterable. I tried iter.contains("my string"), but it does not work. Any idea?

We need additional informations (just like this comment needs more data about what kind of data we need). — Pshemo, Jun 18 '13 at 17:59
Can you show some more code? What exactly is that `iter` referring to? — Rohit Jain, Jun 18 '13 at 17:59
http://stackoverflow.com/questions/2925765/why-does-iterator-have-a-contains-method-but-iterable-does-not-in-scala-2-8 — lamilambkin, Jun 18 '13 at 18:03
If the class is actually derived from `Collection` I suppose you can upcast and then call `contains` on the result... — Maarten Bodewes, Jun 18 '13 at 18:04

score 3 · Answer 1 · answered Jun 18 '13 at 18:02

3

Iterable is an interface, it doesn't contain a method like contains because that would assume the underlying data structure could be read sequentially without corruption.

Neither are assumptions the Iterable interface makes.

answered Jun 18 '13 at 18:02

William Morrison

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score 3 · Answer 2 · answered Jun 18 '13 at 18:09

Your only real option with a bare Iterable is to do a bare for loop:

 for (String string : iterable) {
   if (string.equals(foo)) {
     return true;
   }
 }
 return false;

...or you could call another method which does essentially the same thing, e.g. Guava's Iterables.contains(Iterable, Object).

Björn Höper · Answer 3 · 2013-06-18T18:26:20.457

2

The Interface Iterable only returns an Iterator. So it is not possible to directly obtain if a certain value is inside. Instead you have to iterate using a for-each structure e.g.

boolean found = false;
for (String s: iter) {
    if (s.equals("my string")) {
        found = true;
        break;
    }
 }

Depending on the Size this may not be very efficient. But if its your only choice...it will work at least.

edited Jun 18 '13 at 18:26

answered Jun 18 '13 at 18:13

Björn Höper

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Multiple mistakes in there, Björn, such as `string` instead of `String` and using `==` instead of `equals()` on a `String`. – Maarten Bodewes Jun 18 '13 at 18:15
@owlstead: You are right. Thanks for the comment! I corrected the errors. – Björn Höper Jun 18 '13 at 18:27

score 0 · Accepted Answer · answered Jun 18 '13 at 18:04

0

try with

iter.toString().toLowerCase().equals("my string")

answered Jun 18 '13 at 18:04

NFE

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That's not the question, I think he wants to do this without iterating through the elements... Why is a mystery, but there it is. – Maarten Bodewes Jun 18 '13 at 18:05
Ok. I think the problem like he tried to iterate element and compare with `iter` object directly. – NFE Jun 18 '13 at 18:08
@VTT so this was about `Iterator` and not `Iterable`? – Maarten Bodewes Jun 18 '13 at 18:13
2

That is quite an ugly hack which assumes that the specific iterable implements `toString` in a "user-friendly" way. Although it is generally the case you should not rely on that. – assylias Jun 18 '13 at 18:18
Yes . He accepted my answer so I think that He concern with `Iterator` – NFE Jun 18 '13 at 18:19
Yes, you are right. It was my mistake and lack of knowledge. – MTT Jun 18 '13 at 18:30
1

This is a poor solution. The toString function on the iterator iterface doesn't necessarily return the string representation of all its contents. – William Morrison Jun 18 '13 at 18:43

score 0 · Answer 5 · edited May 23 '17 at 10:25

0

try to create a iterator object and there is a contains method for iterators in most programming languages

This is a very similar question that has a been answered here Why does Iterator have a contains method but Iterable does not, in Scala 2.8?

edited May 23 '17 at 10:25

Community

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answered Jun 18 '13 at 18:05

lamilambkin

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Yes, but this was about Java... – Maarten Bodewes Jun 18 '13 at 18:06

I'm looking for a contains like method for iterable

5 Answers5