Inheritance, Interfaces, and Polymorphism - Java for COBOL Programmers - page 120

FIGURE 5.6
The class hierarchy for ErrorMsg , Printfile ErrorMsg , and
PopupErrorMsg .
E RROR M SG C LASS
In this set of classes, ErrorMsg extends TextMessage , while PopupErrorMsg and Print-
fileErrorMsg extend ErrorMsg .
public class ErrorMsg extends TextMessage {
...
public void setErrorMsg (String inputMsg) {
...
}
}
P OPUP E RROR M SG C LASS
public class PopupErrorMsg extends ErrorMsg {
}
P RINTFILE E RROR M SG C LASS
public class PrintfileErrorMsg extends ErrorMsg {
}