Java8 StringJoinerの詳細コード説明

StringJoiner(CharSequence delimiter)

StringJoiner(CharSequence delimiter, CharSequence prefix, CharSequence suffix)

StringJoiner sjr = new StringJoiner(",", "[", "]");
sjr.add("Smart").add("Techie");
System.out.println("The final Joined string is " + sjr);

sjr1.add("Smart").add("Techie");
System.out.println("The final Joined string is " + sjr1);

public StringJoiner add(CharSequence newElement) {
   prepareBuilder().append(newElement);
   return this;
}

private StringBuilder prepareBuilder() {
    if (value != null) {
       value.append(delimiter);
    } else {
       value = new StringBuilder().append(prefix);
    }
    return value;
}