匿名内部类中的方法

Question

    public void run() {
    jmsTemplate.send(new MessageCreator() {
        public Message createMessage(Session session) throws JMSException {
            byte[] buf = createBytesMessage(5120);
            BytesMessage message = session.createBytesMessage();
            message.writeBytes(buf);
            message.setLongProperty("_publish_time", System.currentTimeMillis());
            return message;
        }   
    });
}

I have this code snippet, what I can make out is its using anonymous class. But I am confused upon how the createMessage() method will be called when the run() is invoked by thread?

Also somewhere I read there is nothing like "anonymous class" but instead its "anonymous inner class". Why its like that?

Answer 1

But I am confused upon how the createMessage() method will be called when the run() is invoked by thread?

The jmsTemplate will expect a MessageCreator instance to be passed and it will responsible for calling the MessageCreator's createMessage() method.

Also somewhere I read there is nothing like "anonymous class" but instead its "anonymous inner class". Why its like that?

Yes. The proper definition is anonymous inner class , since there is no such thing as anonymous public class . While local classes are class declarations, anonymous classes are expressions, which means that you define the class in another expression and so they are called inner .

More info:

• How are anonymous classes used in Java ?

Answer 2

It's an "Anonymous inner class" because it isn't a class that stands by itself, it's a class with some abstract method that you've declared within another class.

As for the method itself, before I look up the class I'm assuming that the handler you send it to ( msTemplate ) just accepts an interface with the method createMessage