A Composite

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A Composite

• C Sc 227, Spring 2005

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Composite Design Pattern

• Compose objects into tree structures to represent
  part-whole hierarchies.
• Composite lets clients treat individual objects
  and compositions of objects uniformly

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General Form
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Client

• Portfolio overall new Portfolio("my IRA")
• // Add one leaf
• overall.add(new Stock("Seven Eleven", 500,
  9.15))
• // Build and add a Portfolio to a Portfolio
• Portfolio tech new Portfolio("Tech stocks")
• Stock s1 new Stock("Sun", 20, 30.50)
• tech.add(s1)
• tech.add(new MutualFund("Microsoft", 13, 45.20))
• overall.add(tech)
• // Can update prices
• s1.updatePrice(31.50) // up 50 cents
• // Show all elements with indents
• overall.listAll()

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Desired Output

• my IRA 5762.6
• 500 shares Seven Eleven 4575.0
• Tech stocks 1187.6
• 20 shares Sun 600.0
• 13.0 shares Microsoft 587.6

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Team Activity

• A) Draw the UML Diagram to capture the real
  world example of stocks, mutual funds, and
  portfolios
• List all class names
• Draw the relationships
• Place the listAll method in the correct place
• Place the add method in the correct place
• Place the getValue methods in the correct place

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An Answer
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Implement Asset Commodity

• While the Value of a Portfolio is the sum of all
  assets, the value of a Commodity is the shares
  times the price
• B) Using the UML diagram, write the Java code for
  Asset and Commodity (a leaf)

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Answer

• abstract class Asset
• private String myName
• public Asset(String name)
• myName name
• public String toString()
• return myName " " getValue()
• public abstract double getValue()

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Answer

• abstract class Commodity extends Asset
• private double myUnits
• private double myPrice
• public Commodity(String name, double shares,
  double price)
• super(name)
• myUnits shares
• myPrice price
• public double getValue()
• return myUnits myPrice

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Stock and MutualFund

• C) Implement Mutual Fund and Stock
• D) Implement Portfolio with the getValue method
  only (no listAll)

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Answer

• class Stock extends Commodity
• public Stock(String company, int shares, double
  price)
• super(shares " shares " company, price,
  shares)
• class MutualFund extends Commodity
• public MutualFund(String fund, double shrs,
  double price)
• super(shares " shares " fund, shrs,
  price)

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Answer

• class Portfolio extends Asset
• private ArrayList myAssets
• public static final String INDENT " "
• public Portfolio(String name)
• super(name)
• myAssets new ArrayList()
• public void add(Asset h)
• myAssets.add(h)
• public double getValue()
• double sum 0.0