StringJoiner class provides utility functions to concatenate words

The following code can be improved by StringJoiner class in Java.

String[] names = new String[]{"George", "Sally", "Fred"};
StringBuilder sb = new StringBuilder("[");
for(String name : names){
  sb.append(name).append(":");
}
sb.deleteCharAt(sb.length() - 1);
sb.append("]");
System.out.println(sb.toString()); //=> [George:Sally:Fred]

In the case of StringJoiner class

String[] names = new String[]{"George", "Sally", "Fred"};
StringJoiner sj = new StringJoiner(":", "[", "]");
for(String name : names){
  sj.add(name);
}
System.out.println(sj.toString()); //=> [George:Sally:Fred]

The code has become more concise :-)

Reference
https://cr.openjdk.java.net/~iris/se/11/latestSpec/api/java.base/java/util/StringJoiner.html#