Chapter 13 - Inheritance and Polymorphism

Chapter 13 Inheritance and Polymorphism

Chapter 13 Objectives ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Defining Classes with Inheritance ,[object Object],[object Object],[object Object],[object Object]

Modeling Two Types of Students ,[object Object],[object Object],[object Object],[object Object]

Classes for the Class Roster ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

The Protected Modifier ,[object Object],[object Object],[object Object]

Polymorphism ,[object Object],[object Object],Pet myPet; myPet = new Dog () ; . . . myPet = new Cat () ;

Creating the roster Array ,[object Object],Student roster = new Student [ 40 ] ; . . . roster [ 0 ] = new GraduateStudent () ; roster [ 1 ] = new UndergraduateStudent () ; roster [ 2 ] = new UndergraduateStudent () ; . . .

State of the roster Array ,[object Object]

Sample Polymorphic Message ,[object Object],[object Object],[object Object],for ( int i = 0; i < numberOfStudents; i++ ) { roster [ i ] .computeCourseGrade () ; }

The instanceof Operator ,[object Object],[object Object],int undergradCount = 0; for ( int i = 0; i < numberOfStudents; i++ ) { if ( roster [ i ] instanceof UndergraduateStudent ) { undergradCount++; } }

Inheritance and Member Accessibility ,[object Object]

The Effect of Three Visibility Modifiers

Accessibility of Super from Sub ,[object Object]

Accessibility from Another Instance ,[object Object]

Inheritance and Constructors ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Abstract Superclasses and Abstract Methods ,[object Object],[object Object],[object Object]

Definition: Abstract Class ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Case 1 ,[object Object],[object Object],[object Object]

Case 2 ,[object Object],[object Object],[object Object],[object Object]

Which Approach to Use ,[object Object],[object Object]

Inheritance versus Interface ,[object Object],[object Object],[object Object],[object Object]

Problem Statement ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Overall Plan ,[object Object],[object Object],[object Object],[object Object],[object Object]

Development Steps ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Step 1 Design ,[object Object],[object Object]

Step 1 Code Directory: Chapter13/Step1 Source Files: ComputeGrades.java Program source file is too big to list here. From now on, we ask you to view the source files using your Java IDE.

Step 1 Test ,[object Object],[object Object]

Step 2 Design ,[object Object],[object Object],for each element i in the roster array { output the name of roster [ i ] ; output the test scores of roster [ i ] ; output the course grade of roster [ i ] ; skip to the next line ; }

Step 2 Code Directory: Chapter13/Step2 Source Files: ComputeGrades.java

Step 2 Test ,[object Object],[object Object]

Step 3 Design ,[object Object],[object Object],[object Object],[object Object]

Step 3 Test ,[object Object],[object Object],[object Object]

Step 4 Design ,[object Object],[object Object],get the filename from the user ; if ( the filename is provided ) read in data and build the roster array ; else output an error message ;

The buildRoster Method ,[object Object],set bufReader for input ; while ( !done ) { line = get next line ; if ( line is END ) { done = true ; } else { student = createStudent ( line ) ; if ( student != null ) { roster [ studentCount ] = student; //add to roster studentCount++; } }

The createStudent Method ,[object Object],StringTokenizer parser = new StringTokenizer ( line ) ; String type; try { type = parser.nextToken () ; if ( type.equals ( UNDER_GRAD ) || type.equals ( GRAD )) { student = newStudentWithData ( type, parser ) ; } else { //invalid type is encountered student = null ; } } catch ( NoSuchElementException e ) { //no token student = null ; } return student;

Step 5: Finalize and Improve ,[object Object],[object Object],[object Object],[object Object],[object Object]

Chapter 13 - Inheritance and Polymorphism

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Chapter 13 - Inheritance and Polymorphism

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