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

[Alex Macdonald]

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
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