question: public static int indexOfIgnoreCase ( String src , String sub , int startIndex , int endIndex ) { if ( startIndex < 0 ) { startIndex = 0 ; } int srclen = src . length ( ) ; if ( endIndex > srclen ) { endIndex = srclen ; } int sublen = sub . length ( ) ; if ( sublen == 0 ) { return startIndex > srclen ? srclen : startIndex ; } sub = sub . toLowerCase ( ) ; int total = endIndex - sublen + 1 ; char c = sub . charAt ( 0 ) ; mainloop : for ( int i = startIndex ; i < total ; i ++ ) { if ( Character . toLowerCase ( src . charAt ( i ) ) != c ) { continue ; } int j = 1 ; int k = i + 1 ; while ( j < sublen ) { char source = Character . toLowerCase ( src . charAt ( k ) ) ; if ( sub . charAt ( j ) != source ) { continue mainloop ; } j ++ ; k ++ ; } return i ; } return - 1 ; }
target:  Finds first index of a substring in the given source string and range with ignored case.