java-native-access/jna · error · UnsupportedOperationException

remove

Error message

remove

What it means

IComEnumVariantIterator implements Iterator purely so an IEnumVARIANT can be used in for-each loops, but the underlying enumeration cannot remove elements. Calling remove() throws UnsupportedOperationException with message "remove".

Source

Thrown at contrib/platform/src/com/sun/jna/platform/win32/COM/IComEnumVariantIterator.java:134

            backingIteration.Release();
            backingIteration = null;
        }
    }

    @Override
    protected void finalize() throws Throwable {
        close();
        super.finalize();
    }

    @Override
    public Iterator<Variant.VARIANT> iterator() {
        return this;
    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException("remove");
    }
}

View on GitHub (pinned to d036ad9781)

Solutions

1. Do not call remove(); collect the items into a list and remove them from that list instead.
2. Use the plain IEnumVARIANT.Next/Reset/Skip APIs directly if mutation of the enumeration is needed.
3. Wrap the loop and catch UnsupportedOperationException if generic code might call remove.

Example fix

// before
for (Variant.VARIANT v : iter) { iter.remove(); }
// after
List<Variant.VARIANT> items = new ArrayList<>();
for (Variant.VARIANT v : iter) { items.add(v); }
items.remove(items.size() - 1);

for (Variant.VARIANT v : comEnumVariantIterator) {
    // never call remove() here; UnsupportedOperationException is guaranteed
}

When it happens

Trigger: Invoking Iterator.remove() (explicitly or implicitly through any collection adapter) on the iterator obtained from an IComEnumVariantIterator.

Common situations: Generic code that removes items while iterating a Collection/Iterable; refactoring code that assumed a mutable iterator.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• remove
• Output directory NOT sucessfully created to: <comRootDir>
• Commandline parameter not found: <key>
• advise: Interface must define a value for either iid via the
• ComInterface must define a value for iid

AI-assisted analysis of java-native-access/jna@d036ad9781 (2026-09-12). Data as JSON: /api/errors/db0268484a56a8ee. Report an issue: GitHub.