String join()

    /**
     * Creates a new String by putting each element together joined by the delimiter. If an element is null, then "null" is used as string to join.
     *
     * @param delimiter
     *          Used as joiner to put elements together
     * @param elements
     *          Elements to be joined
     * @return string of joined elements by delimiter
     * @throws NullPointerException
     *          if one of the arguments is null
     *
     */
    public static String join(CharSequence delimiter, CharSequence... elements) {
        StringJoiner stringJoiner = new StringJoiner(delimiter);

        for (CharSequence element : elements) {
            stringJoiner.add(element);
        }

        return stringJoiner.toString();
    }

List names=new ArrayList<String>();

names.add("1");

names.add("2");

names.add("3");

System.out.println(String.join("-", names));

 

String[] arrStr=new String[]{"a","b","c"};

System.out.println(String.join("-", arrStr));


输出：
1-2-3
a-b-c