I'm intermittently seeing this in my jtreg runs.
Tests pass, but the spam is disconcerting.

[2018-03-08 15:31:35,626] Agent[1]: stdout: MyInflater had end() called
[2018-03-08 15:31:35,626] Agent[1]: stderr: java.lang.Exception: Stack trace
[2018-03-08 15:31:35,627] Agent[1]: stderr: at java.base/java.lang.Thread.dumpStack(Thread.java:1437)
[2018-03-08 15:31:35,627] Agent[1]: stderr: at ConstructInflaterOutput.fail(ConstructInflaterOutput.java:141)
[2018-03-08 15:31:35,627] Agent[1]: stderr: at ConstructInflaterOutput.fail(ConstructInflaterOutput.java:142)
[2018-03-08 15:31:35,627] Agent[1]: stderr: at ConstructInflaterOutput$MyInflater.end(ConstructInflaterOutput.java:39)
[2018-03-08 15:31:35,627] Agent[1]: stderr: at java.base/java.util.zip.Inflater$InflaterZStreamRef$FinalizableZStreamRef.finalize(Inflater.java:501)
[2018-03-08 15:31:35,627] Agent[1]: stderr: at java.base/java.lang.System$2.invokeFinalize(System.java:2094)
[2018-03-08 15:31:35,627] Agent[1]: stdout: MyDeflater had end() called
[2018-03-08 15:31:35,627] Agent[1]: stderr: at java.base/java.lang.ref.Finalizer.runFinalizer(Finalizer.java:87)
[2018-03-08 15:31:35,627] Agent[1]: stderr: at java.base/java.lang.ref.Finalizer.access$100(Finalizer.java:34)
[2018-03-08 15:31:35,627] Agent[1]: stderr: at java.base/java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:171)
[2018-03-08 15:31:35,628] Agent[1]: stderr: java.lang.Exception: Stack trace
[2018-03-08 15:31:35,628] Agent[1]: stderr: at java.base/java.lang.Thread.dumpStack(Thread.java:1437)
[2018-03-08 15:31:35,628] Agent[1]: stderr: at ConstructDeflaterInput.fail(ConstructDeflaterInput.java:164)
[2018-03-08 15:31:35,628] Agent[1]: stderr: at ConstructDeflaterInput.fail(ConstructDeflaterInput.java:165)
[2018-03-08 15:31:35,628] Agent[1]: stderr: at ConstructDeflaterInput$MyDeflater.end(ConstructDeflaterInput.java:39)
[2018-03-08 15:31:35,628] Agent[1]: stderr: at java.base/java.util.zip.Deflater$DeflaterZStreamRef$FinalizableZStreamRef.finalize(Deflater.java:663)
[2018-03-08 15:31:35,628] Agent[1]: stderr: at java.base/java.lang.System$2.invokeFinalize(System.java:2094)
[2018-03-08 15:31:35,628] Agent[1]: stderr: at java.base/java.lang.ref.Finalizer.runFinalizer(Finalizer.java:87)
[2018-03-08 15:31:35,628] Agent[1]: stderr: at java.base/java.lang.ref.Finalizer.access$100(Finalizer.java:34)
[2018-03-08 15:31:35,628] Agent[1]: stderr: at java.base/java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:171)