This one got discussed to death on Reddit, and I know you were there, so
not sure why we're restarting the discussion here, but...
But in any case, to summarize (and at this point this is mostly
theoretical, since any action on this would be a while off): yes, in
theory, it is possible. The mutable state can move into the
byte/character array leaving String with a footprint of a single oop
(which would have to not be shared.) (The word "can" there is doing a
lot of lifting.) There would be a LOT of other work throughout the
platform required to make it possible, and for any perturbation to even
some minor aspect of String performance, there is some critical
application that is highly tuned around that assumption.
The benefit of bringing the character data one hop closer to where it is
consumed is real. But the very large price tag (do you know how much
code there is in the VM to special-case String?) and the potential
performance regressions in corner cases (even if overall performance is
improved) means we would want to proceed with extreme caution here, and
it is not anywhere near the top of the priority list.
On 8/29/2026 12:14 PM, David Alayachew wrote:
Hello @valhalla-dev<[email protected]>,
I was just watching the Inside Java Podcast, episode 68, and at 16:35 [1],
they start talking about operator overloading, mentioning at 17:53 [2] that
String can't be a value class.
I've heard bits and pieces of the why behind this claim, here and there,
something to do with hashCode. So, I looked at the source code for String
[3].
I see 2 mutable fields -- private int hash [4] and private boolean
hashIsZero [5]. But assuming that JEP 531: Lazy Constants (Third Preview)
[6] goes live, that should allow these 2 to be final fields.
I know there are other things required to be a value class, but I don't see
where String would fail those pre-requisites.
But let me first ask -- Is it true that String can't become a value class?
And if so, why not?
Thank you for your time.
David Alayachew
[1] =https://youtu.be/qGRAWfLLJFQ?si=vRZ_I_2BzRT0jh0D&t=995
[2] =https://youtu.be/qGRAWfLLJFQ?si=2PrN0Af_vys1Jtif&t=1073
[3] =
https://github.com/openjdk/jdk/blob/5962d86603a98a0f83aad6fcd6e9dcf90182504e/src/java.base/share/classes/java/lang/String.java
[4] =
https://github.com/openjdk/jdk/blob/5962d86603a98a0f83aad6fcd6e9dcf90182504e/src/java.base/share/classes/java/lang/String.java#L206
[5] =
https://github.com/openjdk/jdk/blob/5962d86603a98a0f83aad6fcd6e9dcf90182504e/src/java.base/share/classes/java/lang/String.java#L214
[6] =https://openjdk.org/jeps/531
