The Publish/Subscribe Framework
All the programming concepts explained so far involved data that needed to be processed. Regardless of the form in which data is provided, the Java programs we’ve written so far took that data, modified it, and printed the results, whether to the console, to files, or to another software component. You could say that all of these components were communicating with each other and passing processed data from one to another. Figure 12-1 abstractly describes interactions among Java components in a program.