1. © 2006 Pearson Addison-Wesley. All rights reserved 8.1.1 Inheritance When one class inherits another class, the new class becomes a specialized version of the original. Java Syntax public class subclass extends superclass {... } public class subclass extends superclass {... } UML (class diagram) Notation

2. © 2006 Pearson Addison-Wesley. All rights reserved 8.1.2 public class RedDot extends Oval { public RedDot( int x, int y, int d ) { super(x, y, d, d); setBackground( Color. red ); } public class RedDot extends Oval { public RedDot( int x, int y, int d ) { super(x, y, d, d); setBackground( Color. red ); } RedDot dotty; dotty = new RedDot(10, 20, 5); theWindow.add(dotty, 0); dotty.repaint(); // methods such as setSize and setLocation // are also available on dotty. Client code

3. © 2006 Pearson Addison-Wesley. All rights reserved 8.1.3 public class BasicCheckbook { protected int balance; // in cents /** post balance == bd*100 + bc */ public BasicCheckbook(int bd, int bc) { balance = bd*100 + bc; } /** post balance == balance@pre + dd*100 + dc */ public void deposit(int dd, int dc) { balance = balance + dd*100 + dc; } /** post balance == balance@pre - (wd*100 + wc) */ public void withdraw(int wd, int wc) { balance = balance - (wd*100 + wc); } /* post result == balance */ public int balanceInCents() { return balance; } public class BasicCheckbook { protected int balance; // in cents /** post balance == bd*100 + bc */ public BasicCheckbook(int bd, int bc) { balance = bd*100 + bc; } /** post balance == balance@pre + dd*100 + dc */ public void deposit(int dd, int dc) { balance = balance + dd*100 + dc; } /** post balance == balance@pre - (wd*100 + wc) */ public void withdraw(int wd, int wc) { balance = balance - (wd*100 + wc); } /* post result == balance */ public int balanceInCents() { return balance; } BasicCheckbook # balance : int «constructor» + BasicCheckbook( int, int) «update» + deposit( int, int) + withdraw( int, int) «query» + balanceInCents() : int

4. © 2006 Pearson Addison-Wesley. All rights reserved 8.1.4 public class CheckbookWithStrBalance extends BasicCheckbook { public CheckbookWithStrBalance(int bd, int bc) { super(bd, bc); } public String toString() { String dollarStr, centStr; int cents; dollarStr = "" + (balance / 100); cents = balance % 100; if (cents < 10) { centStr = "0" + cents; } else { centStr = "" + cents; } return "$" + dollarStr + "." + centStr; } public class CheckbookWithStrBalance extends BasicCheckbook { public CheckbookWithStrBalance(int bd, int bc) { super(bd, bc); } public String toString() { String dollarStr, centStr; int cents; dollarStr = "" + (balance / 100); cents = balance % 100; if (cents < 10) { centStr = "0" + cents; } else { centStr = "" + cents; } return "$" + dollarStr + "." + centStr; } BasicCheckbook # balance : int «constructor» + BasicCheckbook( int, int) «update» + deposit( int, int) + withdraw( int, int) «query» + int balanceInCents() CheckbookWithStrBalance «constructor» + CheckbookWithStr...( int, int) «query» + String toString()

5. © 2006 Pearson Addison-Wesley. All rights reserved 8.1.5 public class CheckbookWithTotals extends CheckbookWithStrBalance { protected int depositTot, withdrawTot; public CheckbookWithTotals(int bd, int bc) { super(bd, bc); depositTot = 0; withdrawTot = 0; } public void deposit(int dd, int dc) { super.deposit(dd, dc); depositTot = depositTot + dd*100 + dc; } public void withdraw(int wd, int wc) { super.withdraw(wd, wc); withdrawTot = withdrawTot - (wd*100 + wc); } public int deposits() { return depositTot; } public int withdraws() { return withdrawTot; } public class CheckbookWithTotals extends CheckbookWithStrBalance { protected int depositTot, withdrawTot; public CheckbookWithTotals(int bd, int bc) { super(bd, bc); depositTot = 0; withdrawTot = 0; } public void deposit(int dd, int dc) { super.deposit(dd, dc); depositTot = depositTot + dd*100 + dc; } public void withdraw(int wd, int wc) { super.withdraw(wd, wc); withdrawTot = withdrawTot - (wd*100 + wc); } public int deposits() { return depositTot; } public int withdraws() { return withdrawTot; } BasicCheckbook # int balance «constructor» + BasicCheckbook( int, int) «update» + deposit( int, int) + withdraw( int, int) «query» + int balanceInCents() CheckbookWithStrBalance «constructor» + CheckbookWith...( int, int) «query» + String toString() CheckbookWithTotals # int depositTot # int withdrawTot «constructor» + CheckbookWithTotals( int, int) «update» + deposit( int, int) + withdraw( int, int) «query» + int deposits() + int withdraws()

6. © 2006 Pearson Addison-Wesley. All rights reserved 8.1.6 public class CheckbookWithRedInk extends CheckbookWithTotals { public CheckbookWithRedInk(int bd, int bc) { super(bd, bc); } public void deposit(int dd, int dc) { super.deposit(dd, dc); if (dd*100+dc < 0 && balance < 0) { System.out.println("$10 surcharge"); balance = balance - 1000; } public void withdraw(int wd, int wc) { super.withdraw(wd, wc); if (wd*100+wc > 0 && balance < 0) { System.out.println("$10 surcharge"); balance = balance - 1000; } public String toString() { String str; if (balance >= 0) { str = super.toString(); } else { balance = -balance; str = "(" + super.toString() + ")"; balance = -balance; } return str; } public class CheckbookWithRedInk extends CheckbookWithTotals { public CheckbookWithRedInk(int bd, int bc) { super(bd, bc); } public void deposit(int dd, int dc) { super.deposit(dd, dc); if (dd*100+dc < 0 && balance < 0) { System.out.println("$10 surcharge"); balance = balance - 1000; } public void withdraw(int wd, int wc) { super.withdraw(wd, wc); if (wd*100+wc > 0 && balance < 0) { System.out.println("$10 surcharge"); balance = balance - 1000; } public String toString() { String str; if (balance >= 0) { str = super.toString(); } else { balance = -balance; str = "(" + super.toString() + ")"; balance = -balance; } return str; } BasicCheckbook # int balance «constructor» + BasicCheckbook( int, int) «update» + deposit( int, int) + withdraw( int, int) «query» + int balanceInCents() CheckbookWithStrBalance «constructor» + CheckbookWith...( int, int) «query» + String toString() CheckbookWithTotals # int depositTot # int withdrawTot «constructor» + CheckbookWithTotals( int, int) «update» + deposit( int, int) + withdraw( int, int) «query» + int deposits() + int withdraws()

7. © 2006 Pearson Addison-Wesley. All rights reserved 8.1.7 public class Driver{ private CheckbookWithRedInk checkbook; public Driver() { checkbook = new CheckbookWithRedInk( 100, 0 ); checkbook.deposit( 20, 0 ); checkbook.withdraw( 125, 99 ); System.out.println("Final Balance: " + checkbook.toString()); } public class Driver{ private CheckbookWithRedInk checkbook; public Driver() { checkbook = new CheckbookWithRedInk( 100, 0 ); checkbook.deposit( 20, 0 ); checkbook.withdraw( 125, 99 ); System.out.println("Final Balance: " + checkbook.toString()); } CheckbookWithRedInk # int balance # int depositTot # int withdrawTot «constructor» + CheckbookWithRedInk( int, int) «update» + deposit( int, int) + withdraw( int, int) «query» + int balanceInCents() + String toString() + int deposits() + int withdraws() A flattened version of the class A client