CODEWITHSUNDEEP
javaconcatenationstring-concatenation
Jon Onstott
Jon Onstott

Reputation: 13727

When is StringBuffer/StringBuilder not implicitly used by the compiler?

I've heard that the compiler (or was it the JVM?) will automatically use a StringBuilder for some string concatenation. When is the right time to explicitly declare one? I don't need a StringBuffer for being thread-safe.

Thanks.

Upvotes: 9

Views: 2053

Answers (1)

Jon Skeet
Jon Skeet

Reputation: 1500225

The compiler will use it automatically for any string concatenation using "+".

You'd usually use it explicitly if you wanted to concatenate in a loop. For example:

StringBuilder builder = new StringBuilder();
for (String name : names)
{
    builder.append(name);
    builder.append(", ");
}
if (builder.length() > 0)
{
    builder.setLength(builder.length() - 2);
}
System.out.println("Names: " + builder);

Another situation would be where you wanted to build up a string over multiple methods, or possibly conditionalise some bits of the building. Basically, if you're not building the string in a single statement (where the compiler can help you) you should at least consider using StringBuilder.

Upvotes: 15

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