How to get the substring that contains the first N unicode characters in Java

Question

The String datatype in Java lets us know how many unicode chars exit in a string by codePointCount; and how to get the n-th unicode char by codePointAt. I was wonding if there is an API to get the substring that contains the first N unicode characters in Java.

Thanks,

Answer 1

There's not a method that does it in one call, but offsetByCodePoints() will help you do this.

static String substring(String str, int idx, int len) {
  return str.substring(idx, str.offsetByCodePoints(idx, len));
}

Answer 2

See java source at: java.util.stream.Collectors#joining()

.codePoints().limit(255) // limit as you need
    .collect(StringBuilder::new, StringBuilder::appendCodePoint, null)