MemoryNotificationInfo instantiation usually(always?) include instantiation of MemoryUsage. MemoryNotificationInfo::from method however allows to accept data that is not correct for MemoryUsage creation.

MemoryUsage constructor asserts "IllegalArgumentException - if used is greater than the value of committed".
https://download.java.net/java/early_access/jdk18/docs/api/java.management/java/lang/management/MemoryUsage.html#%3Cinit%3E(long,long,long,long)

Also this expectation is mentioned at the top level
https://download.java.net/java/early_access/jdk18/docs/api/java.management/java/lang/management/MemoryUsage.html
"'committed' will always be greater than or equal to 'used'"

Specification and OpenJDK implementation of MemoryNotificationInfo::from should follow MemoryUsage specification and reject incorrect data.

At the moment the following is possible with OpenJDK.

=========
        CompositeType usage = new CompositeType("usage", "descr",
                new String[]{"committed", "init", "max", "used"},
                new String[]{"description", "description", "description", "description"},
                new OpenType[]{SimpleType.LONG, SimpleType.LONG, SimpleType.LONG, SimpleType.LONG});

        CompositeType compositeType =
                new CompositeType("typeName", "description",
                        new String[]{"poolName", "usage", "count"},
                        new String[]{"descr 1", "descr 2", "descr 3"},
                        new OpenType[]{SimpleType.STRING, usage, SimpleType.LONG});

        String poolName = "The pool name";
        long committed = 123L;
        long init = 546L;
        long max = 999999L;
        long used = 5555L;
        long count = 123456789L;

        MemoryNotificationInfo createdMNI = MemoryNotificationInfo.from(
                new CompositeDataSupport(compositeType,
                        Map.of(
                                "poolName", poolName,
                                "usage", new CompositeDataSupport(usage, Map.of(
                                        "committed", committed,
                                        "init", init,
                                        "max", max,
                                        "used", used)),
                                "count", count
                        )
                ));
=========

Here above " 'used' is greater than the value of 'committed' " which potentially leads to creation of an incorrect MemoryUsage instance