Bug 44318 annotation hovers don't show up
...if Preferences-->Java-->Editor-->Annotations-->Analyze annotations while typing is turned off. upon saving/compiling files the yellow and red underlines for warnings and errors show up, but not the hovers.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/text/java/hover/AnnotationHover.java
IAnnotationModel model= provider.getAnnotationModel(getEditor().getEditorInput());
		
		if (model != null) {
			Iterator e= new JavaAnnotationIterator(model, true);
			int layer= -1;
			String message= null;
			while (e.hasNext()) {
				Annotation a= (Annotation) e.next();
				if (a instanceof IAnnotationExtension) {
					AnnotationPreference preference= getAnnotationPreference((IAnnotationExtension)a);
					if (preference == null || !(fStore.getBoolean(preference.getTextPreferenceKey()) || (preference.getHighlightPreferenceKey() != null && fStore.getBoolean(preference.getHighlightPreferenceKey()))))
						continue;
				}
				Position p= model.getPosition(a);
				if (a.getLayer() > layer && p != null && p.overlapsWith(hoverRegion.getOffset(), hoverRegion.getLength())) {
					String msg= ((IJavaAnnotation) a).getMessage();
					if (msg != null && msg.trim().length() > 0) {
						message= msg;
						layer= a.getLayer();
					}
				}
			}
			if (layer > -1)
				return formatMessage(message);
		}
		
		return null;
	}
	
	/*