Quick start programming on Netbeans platform

Question

I am learning how to develop a desktop application based on Netbeans Platform Application, so I have started with the famous Quick start tutorial, I have been blocked to understand that piece of code (Netbeans 8.0 platform developers can get it):

private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         
       String enteredText = text.getText();
        Collection<? extends WordFilter> allFilters = Lookup.getDefault().lookupAll(WordFilter.class);
        StringBuilder sb = new StringBuilder();
        for (WordFilter textFilter : allFilters) {
            String processedText = textFilter.process(enteredText);
            sb.append(processedText).append("\n");
        }
        text.setText(sb.toString());
    } 

What I did not understand and of course it is the reason of an execution problem with my code is the line: Collection allFilters = Lookup.getDefault().lookupAll(WordFilter.class);

Can anyone explain it to me, what lookup is? and what that way of using Collection is? (there is no explanation in the tutorial).

Answer 1

Here is the documentation for Lookup class. Please take a look.

The Collection construction means a collection of objects who's classes extend the WordFilter class (or implements the WordFilter interface, in case WordFilter is an interface).