Java Interface used with Callbacks.

Java Interface as Callbacks

• Callbacks are methods that will be invoked when an event of a kind happens.
• It could be for instance a method that you have to put code in when a button is pressed.
• You have to build your own callbacks in Java.
  Callback method example:

  interface TextReceiver {
    void receiveText(String text);
  }
  class TickerTape implements TextReceiver {
    public void receiveText(String text) {
      System.out.println("TICKER: " + text);
    }
  }
  
  public class TextSource {
    // Reference to the implemented Interface
    TextReceiver receiver;  
    TextSource(TextReceiver r) {
      receiver = r;
    }
    public void sendText(String s) {
      receiver.receiveText(s);
    }
    public static void main(String[] args) {
  // Create a object of the class that implements the interface
      TickerTape tickerTape = new TickerTape(); 
      TextSource myCar = new TextSource(tickerTape);
  // Send a text message, which is our event.
      myCar.sendText("Hallo");
    }
  }
  

  The result of this is:

  TICKER: Hallo

  You can download this example here (needed tools can be found in the right menu on this page).