Summary

javax.management.monitor.CounterMonitorMBean documents the return value of getDerivedGaugeTimeStamp as possibly returning null, where it should be zero (this a long value).

Problem

Simple error in API docs.

Solution

Update API docs.

Specification

Diff: src/java.management/share/classes/javax/management/monitor/CounterMonitorMBean.java:

@@ -97,7 +97,7 @@ public interface CounterMonitorMBean extends MonitorMBean {
      *
      * @param object the MBean for which the derived gauge timestamp is to be returned
      * @return The derived gauge timestamp for the specified MBean if this MBean
-     *         is in the set of observed MBeans, or <code>null</code> otherwise.
+     *         is in the set of observed MBeans, or <code>0</code> otherwise.
      *
      */
     public long getDerivedGaugeTimeStamp(ObjectName object);

Github reference: https://github.com/openjdk/jdk/pull/25694