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copied!<p>The polymorphism example. Not sure if the functionally is exactly what you need, but you can see the whole idea (I hope). See the showAllFormat() method of Billfold class.</p> <p>The whole point is inside different format() methods of the DriverLicense and IDCard. Depending on the 'real' (or initially assigned) object the different method will be called even if you just only refer to 'Card' class.</p> <p>NOTE: You didn't provide your DriverLicense implementation, and my is just from head. I have a bit different constructor to show this sub-classes may be totally different.</p> <pre><code>import java.util.ArrayList; import java.util.List; class Billfold { List<Card> list = new ArrayList<Card>(10); void addCard(Card card) // Q: Not sure if this should be String // A: You would like to add a Card { list.add(card); } void showAllFormat() { // go polymorphism !... // when you call this general 'format()' you see the subclasses // 'format()' is executed, not from 'Card' class for(Card x: list) { System.out.println(x.format()); } } } class Card { private String name; /* owner */ public Card() //This is my superclass { name = ""; } public Card(String n) { name = n; } public String getName() { return name; } public boolean isExpired() { return false; } public String format() { return "Card holder: " + name; } } class IDCard extends Card { //This is one of my subclasses private int IDNumber; public IDCard(String n, int id) { super(n); this.IDNumber = id; } public String format() { return "(ID)" + super.format() + " " + IDNumber; } } class DriverLicense extends Card { private String type; public DriverLicense(String n, String type) { super(n); this.type = type; } public String format() { return "(DL)" + super.format() + " TYPE: " + type; } } public class BillfoldTester { public static void main(String[] args) { Card x = new IDCard("Julie", 1995); Card j = new DriverLicense("Jess", "AB"); Billfold bf = new Billfold(); bf.addCard(x); bf.addCard(j); bf.showAllFormat(); } } </code></pre>

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