Get the last three chars from any string - Java

Question

I'm trying to take the last three chracters of any string and save it as another String variable. I'm having some tough time with my thought process.

String word = "onetwotwoone"
int length = word.length();
String new_word = id.getChars(length-3, length, buffer, index);

I don't know how to use the getChars method when it comes to buffer or index. Eclipse is making me have those in there. Any suggestions?

Answer 1

Why not just String substr = word.substring(word.length() - 3)?

Update

Please make sure you check that the String is at least 3 characters long before calling substring():

if (word.length() == 3) {
  return word;
} else if (word.length() > 3) {
  return word.substring(word.length() - 3);
} else {
  // whatever is appropriate in this case
  throw new IllegalArgumentException("word has fewer than 3 characters!");
}

Answer 2

I would consider right method from StringUtils class from Apache Commons Lang: http://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/StringUtils.html#right(java.lang.String,%20int)

It is safe. You will not get NullPointerException or StringIndexOutOfBoundsException.

Example usage:

StringUtils.right("abcdef", 3)

You can find more examples under the above link.

Answer 3

Here's some terse code that does the job using regex:

String last3 = str.replaceAll(".*?(.?.?.?)?$", "$1");

This code returns up to 3; if there are less than 3 it just returns the string.

This is how to do it safely without regex in one line:

String last3 = str == null || str.length() < 3 ? 
    str : str.substring(str.length() - 3);

By "safely", I mean without throwing an exception if the string is nulls or shorter than 3 characters (all the other answers are not "safe").

---

The above code is identical in effect to this code, if you prefer a more verbose, but potentially easier-to-read form:

String last3;
if (str == null || str.length() < 3) {
    last3 = str;
} else {
    last3 = str.substring(str.length() - 3);
}