An evalution of OOME situation with NetBeans IDE has shown that AquaTabbedPaneContrastUI instance is holding 425MB with 15762 elements in htmlViews field.

See also the following comments in NB bug:
https://netbeans.org/bugzilla/show_bug.cgi?id=230493#c6

This is a bug in Aqua L&F implementation in JDK 1.7 - when HTML is being used
for JTabbedPane tab titles each update of tab titles creates a new instance of
BasicHTML.Renderer class without discarding previous instances for the same
tab.

See AquaTabbedPaneCopyFromBasicUI.updateHtmlViews(int) - it was copied from
BasicTabbedPaneUI but is missing htmlViews.removeElementAt(index) call from
line 3528

It could be a serious performance problem in NetBeans as we use HTML for tab
titles in Output window.