RFR (XS): 8188245: [Testbug] test/hotspot/jtreg/gc/logging/TestPrintReferences.java can fail

[sangheon.kim]

Hi all,

Could I have some reviews to fix Java 'double' type rounding issue?

The test is trying to compare time spent at a phase and a sum of each 
sub-phases, but the add and subtract operation of 'double' type can 
result in rounding issue.
e.g.
double phaseTime=14.7;
double total = 14.8;
double result = phaseTime - total;
// result = -0.10000000000000142 but the test is expecting -0.1 so fails.

My proposal is to use BigDecimal whenever those operations are needed.

CR: https://bugs.openjdk.java.net/browse/JDK-8188245
Webrev: http://cr.openjdk.java.net/~sangheki/8188245/webrev.0/
Testing: JPRT, total of 400 iterations of TestPrintReferences.java

Thanks,
Sangheon