A DESCRIPTION OF THE PROBLEM :
The JavaDoc for javax.management.monitor.CounterMonitorMBean.getDerivedGaugeTimeStamp(ObjectName) method contains a documentation error. The method signature shows a return type of 'long' (primitive type), but the JavaDoc states it returns "null" for non-observed MBeans. Since primitive types cannot be null in Java, this is impossible and misleading.

The actual implementation returns 0 (zero) for non-observed objects, not null as documented.


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import java.lang.management.ManagementFactory;
import javax.management.ObjectName;
import javax.management.monitor.CounterMonitor;
import javax.management.monitor.CounterMonitorMBean;

public class CounterMonitorMBeanTest {
    public static void main(String[] args) throws Exception {
        CounterMonitorMBean monitor = new CounterMonitor();
        ManagementFactory.getPlatformMBeanServer()
            .registerMBean(monitor, new ObjectName("test:type=Monitor"));
        
        // Query non-existent object
        ObjectName dummy = new ObjectName("dummy:type=dummy");
        long timestamp = monitor.getDerivedGaugeTimeStamp(dummy);
        
        System.out.println("Timestamp: " + timestamp); // Prints: 0
    }
}
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