CS 151 Day 10

Cay S. Horstmann

Day 10 Clicker Question 1

How do you lay out components in a Swing user interface?

1. By dragging and dropping them to the desired place, using a GUI builder tool
2. By specifiying the layout in a text file that is loaded when the GUI is initialized
3. By writing Java code that places the elements in rows and columns of a grid
4. By implementing a layout manager

Day 10 Clicker Question 2

The Arrays.sort(Object[]) method can sort an array of any objects whose classes implement the Comparable interface type. Of which design pattern is this an example?

1. STRATEGY
2. DECORATOR
3. COMPOSITE
4. None of the above

Day 10 Clicker Question 3

When the COMPOSITE design pattern is applied to Swing containers, a Swing component is a

1. Container
2. Composite
3. Primitive
4. Leaf

Lab

Pattern Discussion

• Is a ShapeIcon from ~/oodp3code/ch04/animation an instance of the DECORATOR pattern?
• Why or why not?

Composite vs. Decorator

• Compare the UML diagrams of the abstract COMPOSITE and DECORATOR patterns.
• Apart from the different class names, what essential difference do you see in the UML diagrams? What does it signify?

A Decorator

• Implement a decorator BoxedIcon that draws a box outside an icon. Leave a ten pixel gap between the original icon and the lines that you draw around it.
• The following code should work:

  import javax.swing.*;
  
  public class IconTester
  {
     public static void main(String[] args)
     {
        JOptionPane.showMessageDialog(
              null, 
              "Hello, Boxed Mars!",
              "Message",
              JOptionPane.INFORMATION_MESSAGE,
              new BoxedIcon(new MarsIcon(50)));
        System.exit(0);
     }
  }

• What is the code of your BoxedIcon class?
• What is method() in the design pattern description in your situation?

Unmodifiable Lists

• One way to satisfy Demeter's law is to use the Collections.unmodifiableList method when returning a list. Read through the javadoc of that method if you aren't familiar with it.
• Look over the Post class in my solution of homework 3. How could you simplify the class by returning an unmodifiable list?
• Is this an example of any of the design patterns that you have seen so far? If so, which? Draw the table with the Name in Design Pattern/Actual Name.

Discussion