Fastest way to put contents of Set<String> to a single String with words separated by a whitespace?

java string optimization set whitespace
Lars Andren picture Lars Andren · Jun 15, 2010 · Viewed 88.6k times · Source

I have a few Set<String>s and want to transform each of these into a single String where each element of the original Set is separated by a whitespace " ". A naive first approach is doing it like this

Set<String> set_1;
Set<String> set_2;

StringBuilder builder = new StringBuilder();
for (String str : set_1) {
  builder.append(str).append(" ");
}

this.string_1 = builder.toString();

builder = new StringBuilder();
for (String str : set_2) {
  builder.append(str).append(" ");
}

this.string_2 = builder.toString();

Can anyone think of a faster, prettier or more efficient way to do this?

Answer

Sean Patrick Floyd picture Sean Patrick Floyd · Jun 15, 2010

With commons/lang you can do this using StringUtils.join:

String str_1 = StringUtils.join(set_1, " ");

You can't really beat that for brevity.

Related questions

Most efficient way to make the first character of a String lower case?

What is the most efficient way to make the first character of a String lower case? I can think of a number of ways to do this: Using charAt() with substring() String input = "SomeInputString"; String output = Character.toLowerCase(input.charAt(0)) + (…

Read More
Fastest way to strip all non-printable characters from a Java String

What is the fastest way to strip all non-printable characters from a String in Java? So far I've tried and measured on 138-byte, 131-character String: String's replaceAll() - slowest method 517009 results / sec Precompile a Pattern, then use Matcher's replaceAll() 637836 results / …

Read More
Using character instead of String for single-character values in StringBuffer append

I was going through the PMD rule AppendCharacterWithChar. It says Avoid concatenating characters as strings in StringBuffer.append. StringBuffer sb = new StringBuffer(); // Avoid this sb.append("a"); // use instead something like this StringBuffer sb = new StringBuffer(); sb.append('a'); Do …

Read More