Bug 42143 Dialogs for source actions do not use dialog font [dialogs]
select a cu in package explorer context menu "Source": "Override/Implement methods..." "Generate Getters and Setters..." "Generate Delegate methods..." "Add constructor from superclass..." "Generate constructor using fields..."
org.eclipse.jdt.ui/ui/org/eclipse/jdt/ui/actions/GenerateNewConstructorUsingFieldsAction.java
private IField[] getSelectedFields(IStructuredSelection selection) {
		List elements= selection.toList();
		int nElements= elements.size();
		if (nElements > 0) {
			IField[] res= new IField[nElements];
			ICompilationUnit cu= null;
			for (int i= 0; i < nElements; i++) {
				Object curr= elements.get(i);
				if (curr instanceof IField) {
					IField fld= (IField) curr;
					if (i == 0) {
						
						cu= fld.getCompilationUnit();
						if (cu == null) {
							return null;
						}
					} else if (!cu.equals(fld.getCompilationUnit())) {
						
						return null;
					}
					try {
						if (fld.getDeclaringType().isInterface()) {
							
							return null;
						}
					} catch (JavaModelException e) {
						JavaPlugin.log(e);
						return null;
					}
					res[i]= fld;