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
* @see IJavaEditorTextHover#setEditor(IEditorPart)
	 */
	public void setEditor(IEditorPart editor) {
		if (editor instanceof CompilationUnitEditor)
			super.setEditor(editor);
		else
			super.setEditor(null);
	}
	/**
	 * Returns the annotation preference for the given marker.
	 * 
	 * @param marker
	 * @return the annotation preference or <code>null</code> if none
	 */	
	private AnnotationPreference getAnnotationPreference(IAnnotationExtension annotation) {
		String markerType= annotation.getMarkerType();
		int severity= annotation.getSeverity();		
		Iterator e= fMarkerAnnotationPreferences.getAnnotationPreferences().iterator();
		while (e.hasNext()) {
			AnnotationPreference info= (AnnotationPreference) e.next();
			if (info.getMarkerType().equals(markerType) && severity == info.getSeverity())
				return info;
			}
		return null;
	}
	static boolean isJavaProblemHover(String id) {
		return PreferenceConstants.ID_PROBLEM_HOVER.equals(id);
	}
}