Check if ArrayList<String> contains part of a string in Java

Question

Say I have an ArrayList:

<string1.4>
<string2.4>
<string3.4>

and I wish to return the first element of the ArrayList that contains "string1" as part of that element's string.
E.g.

arrayList.containsSubString('string1');

How could this be done other than iterating through each of the elements of the ArrayList and checking if "string1" is a substring of that element's string?

what are you allowed to change? do you get a reference to the ArrayList and return the first match or do you have control over the inserting of the data in the list? — Asaf
– Asaf, Commented Jun 21, 2011 at 15:39

aioobe · Accepted Answer · 2011-06-21 15:38:57Z

12

The only way I can think of is doing something like:

strs.get(strs.indexOf(new Object() {
    @Override
    public boolean equals(Object obj) {
        return obj.toString().contains(s);
    }
}));

Don't know if it is considered good practice though.

answered Jun 21, 2011 at 15:38

aioobe

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2 Comments

TookTheRook Over a year ago

Works for my purposes. Thanks! arrayList.toString()!

shareef Over a year ago

great i can use startswith as well

morja · Accepted Answer · 2011-06-21 15:47:11Z

5

With an ArrayList there is no other option than iterating through it. But you could use other data structures like a prefix tree (e.g. a ternary search tree, see this java sample).

edited Jun 21, 2011 at 15:47

answered Jun 21, 2011 at 15:41

morja

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1 Comment

Vishal_Kotecha Over a year ago

java sample link is broken

Ralph · Accepted Answer · 2011-06-21 15:46:44Z

2

I think iterating though the list and checking each item is the fastest way. And it is also the way every one understand your code. (except of building your own data structure).

Anyway you can also use org.apache.commons.collections.CollectionUtils#find(Collection, Predicate)

find(java.util.Collection collection, Predicate predicate) Finds the first element in the given collection which matches the given predicate.

edited Jun 21, 2011 at 15:46

answered Jun 21, 2011 at 15:40

Ralph

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2 Comments

Peter Lawrey Over a year ago

These methods use loops for you.

Ralph Over a year ago

@Peter Lawrey: yes - it is only an way to reuse the compare logic (Predicate) -- Because I understand the question to search for other ways than the traditional for-each-if-check-return way.

jiggy · Accepted Answer · 2011-06-21 15:40:22Z

1

Can't. Even if there was an equivalent of List.contains() it just does a linear search under the hood.

answered Jun 21, 2011 at 15:40

jiggy

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Comments

Peter Lawrey · Accepted Answer · 2011-06-21 15:51:38Z

0

You can use a NavigableSet

NavigableSet<String> set = new TreeSet<String>();
// add strings

String find =
String firstMatch = set.ceiling(find);

answered Jun 21, 2011 at 15:51

Peter Lawrey

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