private static final String and concatenation question

[Edward Winchester]

Hello,

If I have a private static final String in a class, and that String was assigned the result of string concatenation, is it defined whether the concatenation occurs at runtime, or compile time?

e.g.

public class Class {
  private final static String SELECT_SQL = "SELECT * FROM CUSTOMER C " +
                                  "INNER JOIN CUSTOMER_EMAIL CE ON " +
                                  "C.ID = CE.CUSTOMER_ID";
}

I guess it doesn't really matter because the cost is a one-off initialisation cost, but it was something I was wondering about.

Ed

[Henry Wong]

It depends on whether the expression (concat) is a compile time constant or not.

In this case, it is, and hence, the concat occurs at compile time. In fact, since you are assigning it to a final variable at declare time, the static variable is a compile time constant variable. This means that it can be used in another expression, with other constants, and it will still be a compile time constant expression.

Henry

[Edward Winchester]

Thank you Henry.