RFR: 8306697: Add method to obtain String for CONSTANT_Class_info in ClassDesc [v2]

[Chen Liang]

On Wed, 26 Apr 2023 22:10:20 GMT, Mandy Chung <mchung at openjdk.org> wrote:

> What is the issue of calling `ClassDesc.ofDescriptor` for arrays?

Users would have to check the obtained string from a `CONSTANT_Class_info` and call different factory methods, which feels a bit... weird to me, like calling `a == null ? Optional.empty() : Optional.of(a)` instead of `Optional.ofNullable(a)`, and `CONSTANT_Class_info` can be seen as an API provided by the class file as it's defined in the JVMS.

> Have you considered `internalName` to return an `Optional`?

That might be feasible. I initially fear that this may hurt performance-sensitive operations, but now I think as long as we can make `isArray()` or `isClassOrInterface()` constant-foldable (I don't think `String::startsWith` is optimized that far, so might need to check `charAt(0)`), we can still make obtaining the internal name fast.


public Optional<String> internalName() {
    if (!isClassOrInterface()) // assuming constant-foldable
        return Optional.of(descriptorString);
    var internalName = this.internalName; // caching
    if (internalName != null)
        return Optional.of(internalName);
    return Optional.of(this.internalName = descriptorString.substring(1, descriptorString.length() - 1));
}

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PR Comment: https://git.openjdk.org/jdk/pull/13598#issuecomment-1524187441