Exception Handling
Shirley Moore
CS 1401 Spring 2013
cs1401spring2013.pbworks.com
May 7, 2013
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Agenda
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Announcements
Turn in Take-home Quiz 7
String class (for Prog Ex 11.2 and Lab 9)
Assess Programming Exercises 11.1, 11.2
UML Class Diagrams (in detail)
Exception handling
Expectations for Final Exam
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Announcements
• Women in Engineering (WIN) meeting
– Thursday, May 9, 4-6pm
– ACES, Classroom Building
• Lab 9
– Part I will be graded in lab today (must attend to get grade)
– Part 2 on your own before Thursday
– Part 3 will be graded in lab on Thursday
• Plan to post all grades (hw, labs, etc.) by beginning of next week
• Final Exam
– Thursday, May 16, 10:00am-12:45pm
– CCSB 1.0704 (this room)
– Must get 60% on final exam to pass course
• Final Exam Review with Peer Leaders
– Friday, May 10, 10am-? , CCSB 1.0704
• Turn in research mini-projects by Friday, May 17, at the latest.
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String class
• The Java String class provides many methods for creating and
manipulating strings.
• A String object is immutable – i.e., it contents cannot be changed.
• Examples (Try and draw a picture to illustrate):
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String s1 = new String(“Welcome to Java”);
String s2 = “Welcome to Java”);
String s3 = “Welcome to Java”);
if (s1 == s2)
System.out.println(“s1 and s2 are the same object”);
– if (s2 == s3)
System.out.println(“s2 and s3 are the same object”);
– if (s1.equals(s2)
System.out.println(“s1 and s2 have the same contents”);
• See Chapter 9 and/or
http://docs.oracle.com/javase/7/docs/api/java/lang/String.html for
more String class methods.
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Programming Exercise 11.1
• (The Triangle class) Design a class named Triangle that
extends GeometricObject. The class contains:
– Three private double data fields side1, side2, side3 with
default values of 1.
– A no-arg constructor that creates a default triangle.
– A constructor that creates a triangle with specified side1,
side2, and side3.
– The accessor methods for all three data fields.
– A method getArea() that returns the area of the triangle
– A method getPerimeter() that returns the perimeter of the
triangle
– A method toString() that returns a string representation of
the triangle.
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Programming Exercise 11.2
• (The Person, Student, Employee, Faculty, and Staff
classes) Design a class named Person and its two
subclasses named Student and Employee. Make
Faculty and Staff subclasses of Employee. A person has
a name, address, phone number, and email address. A
student has a class status (freshman, sophomore,
junior, senior). Define the status as a constant. An
employee has an office, salary, and date hired. A
faculty member has office hours and a rank. A staff
member has a title. Override the toString method in
each class to display the class name and the person’s
name.
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UML Class Diagrams
• See
http://cs.nmu.edu/~mkowalcz/cs120f08/uml/UMLdiagram.html
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Exception Handling
• Enables a program to deal with exceptional (i.e., error)
situations and continue operation
• Can make programs more reliable
• Examples of exceptions
– Integer division by zero
– Input mismatch (e.g., real number entered when integer was
requested)
– Illegal argument value
• Enable methods to “throw” exceptions back to caller
– Why not just have the method print an error message and exit?
• Caller uses a try-catch block to invoke the method and
handle any exception
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Exception Types
• Exceptions are objects that are defined using
classes.
• Pre-defined exception types in
java.lang.Throwable class
– http://docs.oracle.com/javase/7/docs/api/java/lang/R
untimeException.html
– e.g., ArithmeticException, NullPointerException,
IndexOutOfBoundsException,
IllegalArgumentException
• You can also define your own exception types.
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Examples
• Download from course website:
– QuotientWithException.java (trivial example for
illustration purposes)
– InputMismatchExceptionDemo.java
– Circle3.java (also need GeometricObject.java)
– Circle4.java
– InvalidRadiusException.java
– TestCircles.java
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Class Activity
• Download from course website:
– Projectile.java
– TestProjectile.java
• Modify the program to handle the following
exceptions
– Invalid input
• Initial height must be non-negative
• Initial velocity must be positive
• Angle of inclination must be greater than 0 and less than 90
– Invalid time step interval (must be positive)
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Final Exam
• Comprehensive
• Will target learning outcomes from each unit
• Review guide and practice problems will be
posted by tomorrow.
• Review in class on Thursday
• Review session with Peer Leaders on Friday at
10:00
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