Which class to use for this static method, StringBuffer or StringBuilder?

Question

For the following code, which class should I use in a static method, StringBuilder or StringBuffer? Based on the API, StringBuffer is thread-safe, but StringBuilder is not.

public static String getString(int[] arrs) {
    StringBuilder sb = new StringBuilder();  //1
    StringBuffer sb = new StringBuffer();    //2
    for (int i : arrs) {
        sb.append(i);
    }
    return sb.toString();
}

Answer 1

It's a method-local variable, you won't have concurrent access there... so use StringBuilder

Answer 2

Why worry about thread safety with the code you've shown though? If your StringBuilder isn't being used in a way that requires having to worry about thread safety, then don't spend the overhead required for it needlessly. Use StringBuilder.