RFR: JDK-8322878: Including sealing information Class.toGenericString()

[Joe Darcy]

On Wed, 3 Jan 2024 22:20:15 GMT, Joe Darcy <darcy at openjdk.org> wrote:

>>> Since it doesn't seem possible to do so, I did not attempt to relay "non-sealed" information in this PR :-)
>> 
>> Naively, I thought that something like this is possible _in principle_; I might be mistaken though:
>> 
>> diff --git a/src/java.base/share/classes/java/lang/Class.java b/src/java.base/share/classes/java/lang/Class.java
>> index 851d65d06ad..014845860d0 100644
>> --- a/src/java.base/share/classes/java/lang/Class.java
>> +++ b/src/java.base/share/classes/java/lang/Class.java
>> @@ -4771,6 +4771,30 @@ public boolean isSealed() {
>>          return getPermittedSubclasses() != null;
>>      }
>>  
>> +    private boolean isNonSealed() {
>> +        if (isSealed())
>> +            return false;
>> +        if (!isInterface() && Modifier.isFinal(getModifiers())) {
>> +            // unlike interface, class can be final
>> +            return false;
>> +        }
>> +        // if an ancestor is sealed, this class can either be non-sealed or final
>> +        return hasSealedAncestor(this);
>> +    }
>> +
>> +    private boolean hasSealedAncestor(Class<?> clazz) {
>> +        var superclass = clazz.getSuperclass();
>> +        if (superclass != null) {
>> +            if (superclass.isSealed() || hasSealedAncestor(superclass))
>> +                return true;
>> +        }
>> +        for (var superinterface : clazz.getInterfaces()) {
>> +            if (superinterface.isSealed() || hasSealedAncestor(superinterface))
>> +                return true;
>> +        }
>> +        return false;
>> +    }
>> +
>>      private native Class<?>[] getPermittedSubclasses0();
>>  
>>      /*
>
> Thanks @pavelrappo; I'll explore incorporating functionality like this into the PR, probably next week.

> I think the best place, or least-bad place, to discuss the "modifier" ordering of sealed/non-sealed would be an informative note on Modifier.toString(int) -- "The sealed/non-sealed Java language modifiers are not represented in the class file as access flags and thus not modeled by this class [java.lang.reflect.Modifier] .... sealed/non-sealed should be presented in the same location as final."

Filed JDK-8322979: Add informative discussion to Modifier.

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PR Review Comment: https://git.openjdk.org/jdk/pull/17239#discussion_r1441050656