From off line discussion:
Would be great if window with compile output could filter out warnings and show errors only or provide some other means to quickly navigate in the output. This problem is really annoying for me and likely for other JDK developers who tries to use NB to compile JRE parts. Obviously as JRE developer i have to compile code that uses sun.* and this generates tons of warnings. Finding single error among thousand of warnings is *very* annoying.
Probably requires changes on both sides (console and and logger). Jesse, feel free to reassign.
You can set Ant Verbosity to a less verbose value. (Settings available from button in Output Window.) That affects all builds.
But in this case the problem is the OpenJDK build scripts. These need to be passing a special compiler flag to disable warnings about usage of sun.* packages. I know jdk/make/netbeans/common/shared.xml uses -XDignore.symbol.file=true but I am not sure if this is the right flag or if there is another. (Ideally warnings about sun.* would simply be one -Xlint suboption.)
Note that there is also a bug filed for javac to queue up warning messages and only display them if there are no errors, or at least to put the errors at the top or bottom of the list so they are easy to find. Note also that the NB Ant integration automatically stops scrolling the OW when (what appears to be) the first "hard" error message is printed.
Why was this reopened? Comment #1 explains what needs to happen in OpenJDK build scripts.
As far as I remember Igor wanted to have a filter which can filter out the warnings from the output.
But if the javac Messager will print first errors and then warning. It's OK to keep it as WONTFIX.