RFR: JMC-6256: JMC doesn't respect Long.MIN_VALUE as a missing value

[Erik Gahlin]

Nice work!

We will add N/A values to ThreadPark and OldObjectSample event for JDK 
12, so this will be great!

Erik

> Hi!
>
> This patch addresses JMC-6256 [0], in which MIN_VALUEs are displayed in
> their numeric form instead of being displayed as a N/A or missing value.
> For testing purposes, I have been using the memoryleak.jfr recording that
> is available as an attachment on JMC-6127 [1].
>
> As per the comments in the bug report, there are 6 cases to consider for
> missing values in JMC [2]. Additionally, it may be nice to show the actual
> value in parenthesis in the tooltip [3].
>
> Screenshots (album [4]):
> Before: https://imgur.com/aoGgzRn [5]
> After: https://imgur.com/DVnHQGZ [6]
>
> The culprit here seems to be the way the conditionals in the
> "getValueString()" [7][8] end up processing the value. There is a
> duplication of the "instanceof IDisplayable" in the JfrPropertySheet [7]
> and the TypeHandling [8], and the TypeHandling.getValueString() ends up
> being called anyways in the JfrPropertySheet.getValueString(). As a result,
> the conditional to see if it's an IDisplayable from the JfrPropertySheet
> happens before the conditional to see if it is a min value [9] (which is
> where we want to end up in this case).
>
> This patch removes the duplicated conditional from the JfrPropertySheet,
> because it is already correctly handled in TypeHandling. Additionally, a
> function "getNumericString" has been introduced for the display of the
> tooltip. If the value is an IQuantity then "getNumericString" will figure
> out which missing value type it is, and display it in the tooltip. If the
> value is an IQuantity but not a missing value, then it delegates to
> TypeHandling.getValueString(). I've also included a quick unit test to
> verify the behaviour of "getNumericString".
>
> Thoughts?
>
> Cheers,
>
> Alex
>
> [0] https://bugs.openjdk.java.net/browse/JMC-6256
> [1] https://bugs.openjdk.java.net/browse/JMC-6127
> [2]
> https://bugs.openjdk.java.net/browse/JMC-6256?focusedCommentId=14229297&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14229297
> [3]
> https://bugs.openjdk.java.net/browse/JMC-6256?focusedCommentId=14229296&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14229296
> [4] https://imgur.com/a/3BZNHnG
> [5] https://imgur.com/aoGgzRn
> [6] https://imgur.com/DVnHQGZ
> [7]
> http://hg.openjdk.java.net/jmc/jmc/file/a76a464b3764/application/org.openjdk.jmc.flightrecorder.ui/src/main/java/org/openjdk/jmc/flightrecorder/ui/JfrPropertySheet.java#l307
> [8]
> http://hg.openjdk.java.net/jmc/jmc/file/efeb1e97bec3/core/org.openjdk.jmc.common/src/main/java/org/openjdk/jmc/common/util/TypeHandling.java#l171
> [9]
> http://hg.openjdk.java.net/jmc/jmc/file/efeb1e97bec3/core/org.openjdk.jmc.common/src/main/java/org/openjdk/jmc/common/util/TypeHandling.java#l167