Java编译器字符串优化

Question

It seems reasonable to me that the compiler is going to take something like this:

log.info("A really long logger message that is kind of a pain in the tucous " + 
    "and violates formatting standards by making the line to long");

and compile the two Strings into one. I'm pretty sure this is true but I would like to have my ducks in a row if anyone brings it up.

Answer 1

Yes, this will be handled by the constant expression part of the Java Language Specification. In particular see part 15.18.1. String Concatenation Operator +

Answer 2

Strings computed by constant expressions (§15.28) are computed at compile time and then treated as if they were literals.

Show that quote from the JLS to anyone who 'challenges' you.

Answer 3

To check if what JLS says about constant expressions is true I complied this code, Test.java

public static void main(String[] args) {
    log.warning("123" + "456");
}

then decompile Test.class with Jad and got this

public static void main(String args[])
{
    log.warning("123456");
}

that is, in Test.class there is only one literal "123456"