You can use
org.apache.commons.lang3.StringUtils.containsIgnoreCase(CharSequence str,
CharSequence searchStr);
Checks if CharSequence contains a search CharSequence irrespective of case, handling null. Case-insensitivity is defined as by String.equalsIgnoreCase(String).
A null CharSequence will return false.
This one will be better than regex as regex is always expensive in terms of performance.
For official doc, refer to : StringUtils.containsIgnoreCase
Update :
If you are among the ones who
regex/Pattern based solutions, toLowerCase, you can implement your own custom containsIgnoreCase using java.lang.String.regionMatches
public boolean regionMatches(boolean ignoreCase,
int toffset,
String other,
int ooffset,
int len)
ignoreCase : if true, ignores case when comparing characters.
public static boolean containsIgnoreCase(String str, String searchStr) {
if(str == null || searchStr == null) return false;
final int length = searchStr.length();
if (length == 0)
return true;
for (int i = str.length() - length; i >= 0; i--) {
if (str.regionMatches(true, i, searchStr, 0, length))
return true;
}
return false;
}