Java8 StringJoiner的代码详解

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;
}

public String toString() {
    if (value == null) {
      return emptyValue;
    } else {
    if (suffix.equals("")) {
      return value.toString();
    } else {
    int initialLength = value.length();
    String result = value.append(suffix).toString();
    // reset value to pre-append initialLength
    value.setLength(initialLength);
    return result;
    }
}