Remove last character of a StringBuilder?

Question

When you have to loop through a collection and make a string of each data separated by a delimiter, you always end up with an extra delimiter at the end, e.g.

for (String serverId : serverIds) {   sb.append(serverId);    sb.append(","); } 

Gives something like : serverId_1, serverId_2, serverId_3,

I would like to delete the last character in the StringBuilder (without converting it because I still need it after this loop).

Answer 1

Others have pointed out the deleteCharAt method, but here's another alternative approach:

String prefix = ""; for (String serverId : serverIds) {   sb.append(prefix);   prefix = ",";   sb.append(serverId); } 

Alternatively, use the Joiner class from Guava :)

As of Java 8, StringJoiner is part of the standard JRE.

Answer 2

Another simple solution is:

sb.setLength(sb.length() - 1); 

---

A more complicated solution:

The above solution assumes that sb.length() > 0 ... i.e. there is a "last character" to remove. If you can't make that assumption, and/or you can't deal with the exception that would ensue if the assumption is incorrect, then check the StringBuilder's length first; e.g.

// Readable version if (sb.length() > 0) {    sb.setLength(sb.length() - 1); } 

or

// Concise but harder-to-read version of the above. sb.setLength(Math.max(sb.length() - 1, 0));