question: public static String join ( double [ ] self , String separator ) { StringBuilder buffer = new StringBuilder ( ) ; boolean first = true ; if ( separator == null ) separator = "" ; for ( double next : self ) { if ( first ) { first = false ; } else { buffer . append ( separator ) ; } buffer . append ( next ) ; } return buffer . toString ( ) ; }
target:  Concatenates the string representation of each items in this array, with the given String as a separator between each item.