Aggregation - dynamic composition is referred to as aggregation

Question

Hi,
This has been in my todo forever
Need help to understand the statement "dynamic composition is referred to as aggregation"
Is their an example for this statement. Using an example that most of us work on as part of college project work - WYSIWYG HTML Editor - where the Editor was an aggregation of Text, Paragraph, Bold, Underline etc (the various HTML Tags) and so. Does dynamic composition refers to the fact that the elements to be added to the Editor is determined at Run-time?
This is a statements from "Thinking In Java - 4th Edition" - Page 32. Appreciate your help in clarification
Thanks,
AK

Answer 1

Hi,
Both Aggregation and composition are stronger form of Association and it depicts "Has a" relationship between
classes. The difference between Aggregation and Composition is the lifetime of Composing and composed element.
If Class A has B and class B has a life time only until A exists it's known as "Composition". If class A has class B and
Class B has independent lifetime of its own then it's Aggregation.
public class Editor {
     public Editor()
     public Paragraph getPara() {
          return para;
     public void setPara(Paragraph para) {
          this.para = para;
     public Text getText() {
          return text;
     public void setText(Text text) {
          this.text = text;
     private Paragraph para;
     private Text text;
}Here i can add any paragraph, any text which is a Sub Type of Paragraph and Text to the editor dynamically.
Hope i have clarified something.
Thanks