Option to ignore case with .contains method?

Is there an option to ignore case with .contains() method?

I have an ArrayList of DVD object. Each DVD object has a few elements, one of them is a title. And I have a method that searches for a specific title. It works, but I'd like it to be case insensitive.


If you're using Java 8

List<String> list = new ArrayList<>();

boolean containsSearchStr = list.stream().anyMatch("search_value"::equalsIgnoreCase);

I'm guessing you mean ignoring case when searching in a string?

I don't know any, but you could try to convert the string to search into either to lower or to upper case, then search.

// s is the String to search into, and seq the sequence you are searching for.
bool doesContain = s.toLowerCase().contains(seq);

Edit: As Ryan Schipper suggested, you can also (and probably would be better off) do seq.toLowerCase(), depending on your situation.


private boolean containsIgnoreCase(List<String> list, String soughtFor) {
    for (String current : list) {
        if (current.equalsIgnoreCase(soughtFor)) {
            return true;
        }
    }
    return false;
}

In Java 8 you can use the Stream interface:

return dvdList.stream().anyMatch(d -> d.getTitle().equalsIgnoreCase("SomeTitle"));

This probably isn't the best way for your particular problem, but you can use the String.matches(String regex) method or the matcher equivalent. We just need to construct a regular expression from your prospective title. Here it gets complex.

List<DVD> matchingDvds(String titleFragment) {
    String escapedFragment = Pattern.quote(titleFragment);
    // The pattern may have contained an asterisk, dollar sign, etc.
    // For example, M*A*S*H, directed by Robert Altman.
    Pattern pat = Pattern.compile(escapedFragment, Pattern.CASE_INSENSITIVE);
    List<DVD> foundDvds = new ArrayList<>();
    for (DVD dvd: catalog) {
        Matcher m = pat.matcher(dvd.getTitle());
        if (m.find()) {
            foundDvds.add(dvd);
        }
    }
    return foundDvds;
}

But this is inefficient, and it's being done purely in Java. You would do better to try one of these techniques:

  1. Learn the Collator and CollationKey classes.
  2. If you have no choice but to stay in the Java world, add a method to DVD, boolean matches(String fragment). Have the DVD tell you what it matches.
  3. Use a database. If it supports case-insensitive collations, declare the title column of the DVD table that way. Use JDBC or Hibernate or JPA or Spring Data, whichever you choose.
  4. If the database supports advanced text search, like Oracle, use that.
  5. Back in the Java world, use Apache Lucene and possibly Apache Solr.
  6. Use a language tuned for case-insensitive matches.

If you can wait until Java 8, use lambda expressions. You can avoid the Pattern and Matcher class that I used above by building the regex this way:

   String escapedFragment = Pattern.quote(titleFragment);
   String fragmentAnywhereInString = ".*" + escapedFragment + ".*";
   String caseInsensitiveFragment = "(?i)" + fragmentAnywhereInString;
   // and in the loop, use:
   if(dvd.getTitle().matches(caseInsensitiveFragment)) {
        foundDvds.add(dvd);
    }

But this compiles the pattern too many times. What about lower-casing everything?

if (dvd.getTitle().toLowerCase().contains(titleFragment.toLowerCase()))

Congratulations; you've just discovered the Turkish problem. Unless you state the locale in toLowerCase, Java finds the current locale. And the lower-casing is slow because it has to take into account the Turkish dotless i and dotted I. At least you have no patterns and no matchers.