append or + operator in StringBuffer?

Question

In my project there are some code snippets which uses StringBuffer objects, and the small part of it is as follows

StringBuffer str = new StringBuffer();

str.append("new " + "String()");

so i was confused with the use of append method and the + operator.

ie the following code could be written as

str.append("new ").append("String()");

So are the two lines above same?(functionally yes but) Or is there any particular usage of them? ie performance or readability or ???

thanks.

Answer 1

In that case it's more efficient to use the first form - because the compiler will convert it to:

StringBuffer str = new StringBuffer();
str.append("new String()");

because it concatenates constants.

A few more general points though:

• If either of those expressions wasn't a constant, you'd be better off (performance-wise) with the two calls to append, to avoid creating an intermediate string for no reason
• If you're using a recent version of Java, StringBuilder is generally preferred
• If you're immediately going to append a string (and you know what it is at construction time), you can pass it to the constructor