"Westfw, thanks for giving me a nudge in the right direction!
I had a look, and the Arduino IDE contains \java\bin\javaw.exe
Compiling a list of java versions supplied with IDE versions reveals that IDE 1.8.6 and 1.8.7 share the same version of java.
Arduino IDE version: 1.8.1
javaw.exe version: 8.0.1110.14
Arduino IDE version: 1.8.5
javaw.exe version: 8.0.1440.1
Arduino IDE version: 1.8.6
javaw.exe version: 8.0.1710.11
Arduino IDE version: 1.8.7
javaw.exe version: 8.0.1710.11
Arduino IDE version: beta 1.9
javaw.exe version: 8.0.1910.12
Arduino IDE version: Current hourly build
javaw.exe version: 8.0.1910.12
I then copied the java folder from IDE BETA 1.9 into the IDE 1.8.7 install folder and the fault is gone!
As a double check, I copied the java from 1.8.7 into beta 1.9 and the fault shows up in beta 1.9.
My conclusion is that the java supplied with Arduino IDE 1.8.6 and 1.8.7 (java version 8.0.1910.12) is the cause of the 30% CPU utilisation issue that some of us have seen.
SOLUTION:
You can run Arduino IDE 1.8.7 successfully simply by replacing the java folder, using the Arduino Beta 1.9 install as the source.
Does anyone (that has seen this fault before) care to test and confirm or deny this theory?
Cheers,
Matthew.
CONFIRMATION:I renamed java folder (in "program files\arduino\") to java-old to save it. As we age, we learn how not to break things.
Copied a new java folder from 1.9.0 beta zip file.
I didn't notice fan (A/Cond makes more noise than my fan) but CPU use dropped from >50% as it should.
Now 2% when IDE window looses focus.
2% is much better when IDE window looses focus!!
>10 year old Toshiba L500 with Windows 7 (32 bit)
Laptop was getting sluggish switching to my schematic editor was why I chased this 'feature'
Thanks Mathew.Neil