Why does Java’s URL class not recognize certain protocols?

Issue Java throws a MalformedURLException because it couldn’t find a URLStreamHandler for that protocol. Check the javadocs of the constructors for the details. Summary Since the URL class has an openConnection method, the URL class checks to make sure that Java knows how to open a connection of the correct protocol. Without a URLStreamHandler for … Read more

Difference between paint, paintComponent and paintComponents in Swing

AWT, override paint(). Swing top-level container (e.g.s are JFrame, JWindow, JDialog, JApplet ..), override paint(). But there are a number of good reasons not to paint in a TLC. A subject for a separate question, perhaps. The rest of Swing (any component that derives from JComponent), override paintComponent(). Neither override nor explicitly call paintComponents(), leave … Read more

How to append elements at the end of ArrayList in Java?

Here is the syntax, along with some other methods you might find useful: //add to the end of the list stringList.add(random); //add to the beginning of the list stringList.add(0, random); //replace the element at index 4 with random stringList.set(4, random); //remove the element at index 5 stringList.remove(5); //remove all elements from the list stringList.clear();

How to get Form data as a Map in Spring MVC controller?

You can also use @RequestBody with MultiValueMap e.g. @RequestMapping(value=”/create”, method=RequestMethod.POST, consumes = MediaType.APPLICATION_FORM_URLENCODED_VALUE) public String createRole(@RequestBody MultiValueMap<String, String> formData){ // your code goes here } Now you can get parameter names and their values. MultiValueMap is in Spring utils package

How do I initialize classes with lots of fields in an elegant way?

You can either use a constructor or a builder pattern or a variation of the builder pattern to fix the problem of having too many fields in your initialization step. I’m going to extend your example a bit to prove my point of why these options are useful. Understanding your example: Lets say an Offer … Read more

Java: Is there a difference between L and l (lowercase L) when specifying a long?

No practical difference. Either L or l can be used, both indicate a long primitive. Also, either can be autoboxed to the corresponding Long wrapper type. However, it is worth noting that JLS-3.10.1 – Integer Literals says (in part) An integer literal is of type long if it is suffixed with an ASCII letter L … Read more