Remove last character of a StringBuilder?

java stringbuilder
Matthew picture Matthew · Aug 3, 2010 · Viewed 336.9k times · Source

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

Jon Skeet picture Jon Skeet · Aug 3, 2010

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.

Related questions

Difference between StringBuilder and StringBuffer

What is the main difference between StringBuffer and StringBuilder? Is there any performance issues when deciding on any one of these?

Read More
How can I clear or empty a StringBuilder?

I'm using a StringBuilder in a loop and every x iterations I want to empty it and start with an empty StringBuilder, but I can't see any method similar to the .NET StringBuilder.Clear in the documentation, just the delete …

Read More
How to append a newline to StringBuilder

I have a StringBuilder object, StringBuilder result = new StringBuilder(); result.append(someChar); Now I want to append a newline character to the StringBuilder. How can I do it? result.append("/n"); Does not work. So, I was thinking about writing …

Read More