Does a final String inside a private static method instantiate a new object when invoked?

Question

Does a static final String inside a private static method instantiate a new object when invoked?

private static String Test() {
    final String foo = "string literal";
    return foo;
}

Or does the compiler know there is only a single, string literal, inside the method? Or should I make it a private static final class field? This has the effect of reducing readability by spreading the code around the class.

Answer 1

No, the particular string will be reused from the string literal pool. If it was for example:

final String foo = new String("string literal");

Then indeed a new one will be created everytime the method is invoked.

Here's an evidence:

public static void main(String[] args) throws Exception {
    String s1 = test1();
    String s2 = test1();
    System.out.println(s1 == s2); // true

    String s3 = test2();
    String s4 = test2();
    System.out.println(s3 == s4); // false
}

private static String test1() {
    final String foo = "string literal";
    return foo;
}

private static String test2() {
    final String foo = new String("string literal");
    return foo;
}

Note that the final modifier doesn't have any influence in this particular case. It only prohibits the variable from being reassigned.