More about inheritance - Objects First with Java: A Practical Introduction Using BlueJ - page 314

To make this method more useful, we would typically override it in our own classes. We can,
for example, define the Post ' s display method in terms of a call to its toString method. In
this case, the toString method would not print out the details, but just create a string with the
text. Code 9.3 shows the changed source code.

Code 9.3
toString method
for Post and
MessagePost

public class Post
{

... ..
public String toString()
{

String text = username + "\n" + timeString(timestamp);
if (likes > 0) {
text += " — " + likes + " people like this.\n" ;

}
else {
text += "\n" ;

}

if (comments.isEmpty()) {
return text + " No comments.\n" ;

}
else {
return text + " " + comments.size() +
" comment(s). Click here to view.\n" ;

}

}

public void display()
{

System.out.println(toString());

}

}

public class MessagePost extends Post
{

...
public String toString()
{

return super .toString() + message + "\n" ;

}

public void display()
{

System.out.println(toString());

}

}