Bug 46805 prepare Compare for encoding support
I20031111 The Compare plugin only supports the global workspace encoding. It does not support encodings per file.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/compare/JavaCompareAction.java
String message= MessageFormat.format(errorFormat, new String[] { fJavaElementLabelProvider.getText(element) } );
			
			MessageDialog.openError(shell, errorTitle, message);
			return;
		}
		
		d.compare(new DiffNode(new TypedElement(fLeft, left), new TypedElement(fRight, right)));
		
		fJavaElementLabelProvider.dispose();
		fJavaElementLabelProvider= null;
	}
	
	protected boolean isEnabled(ISelection selection) {
		if (selection instanceof IStructuredSelection) {
			Object[] sel= ((IStructuredSelection) selection).toArray();
			if (sel.length == 2) {
				for (int i= 0; i < 2; i++) {
					Object o= sel[i];
					if (!(o instanceof ISourceReference))
						return false;
				}
				fLeft= (ISourceReference) sel[0];
				fRight= (ISourceReference) sel[1];				
				return true;
			}
		}
		return false;
	}
	private String getExtendedSource(ISourceReference ref) throws JavaModelException {