The Model-View-Controller Architecture - The Definitive Guide to Java Swing - page 59

Figure 3-2. The JTextArea MVC architecture
Sharing Data Models
Because data models store only the state information, you can share a model across multiple
components. Then each component view can be used to modify the model.
In the case of Figure 3-3, three different JTextArea components are used to modify one
Document model. If a user modifies the contents of one JTextArea , the model is changed,
causing the other text areas to automatically reflect the updated document state. It isn't necessary
for any Document view to manually notify others sharing the model.