question: public static String findCommonPrefix ( String ... strings ) { StringBuilder prefix = new StringBuilder ( ) ; int index = 0 ; char c = 0 ; loop : while ( true ) { for ( int i = 0 ; i < strings . length ; i ++ ) { String s = strings [ i ] ; if ( index == s . length ( ) ) { break loop ; } if ( i == 0 ) { c = s . charAt ( index ) ; } else { if ( s . charAt ( index ) != c ) { break loop ; } } } index ++ ; prefix . append ( c ) ; } return prefix . length ( ) == 0 ? StringPool . EMPTY : prefix . toString ( ) ; }
target:  Finds common prefix for several strings. Returns an empty string if arguments do not have a common prefix.