dap4/d4core/src/main/java/dap4/core/util/DapUtil.java
static public String
    join(String[] array, String sep, int from, int upto)
    {
        if(sep == null) sep = "";
        if(from < 0 || upto > array.length)
            throw new IndexOutOfBoundsException();
        if(upto <= from)
            return "";
        StringBuilder result = new StringBuilder();
        boolean first = true;
        for(int i = from; i < upto; i++, first = false) {
            if(!first) result.append(sep);
            result.append(array[i]);
        }
        return result.toString();
    }
static public String
    join(String[] array, String sep, int from, int upto)
    {
        if(sep == null) sep = "";
        if(from < 0 || upto > array.length)
            throw new IndexOutOfBoundsException();
        if(upto <= from)
            return "";
        StringBuilder result = new StringBuilder();
        boolean first = true;
        for(int i = from; i < upto; i++, first = false) {
            if(!first) result.append(sep);
            result.append(array[i]);
        }
        return result.toString();
    }
static public String join ( String [ ] array , String sep , int from , int upto ) { if ( sep == null ) sep = "" ; if ( from < 0 || upto > array . length ) throw new IndexOutOfBoundsException ( ) ; if ( upto <= from ) return "" ; StringBuilder result = new StringBuilder ( ) ; boolean first = true ; for ( int i = from ; i < upto ; i ++ , first = false ) { if ( ! first ) result . append ( sep ) ; result . append ( array [ i ] ) ; } return result . toString ( ) ; }
Given an Array of Strings and a separator and a count,
concat the first count elements of an array with separator
between them. A null string is treated like "".

@param array the array to concat
@param sep   the separator
@param from  start point for join (inclusive)
@param upto  end point for join (exclusive)
@return the join
Given an Array of Strings and a separator and a count concat the first count elements of an array with separator between them . A null string is treated like .