CISC 370 Lecture Notes for Class No. 2, February 10, 2000
Java .vs. C++ and an Object-Oriented Programming Example

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Graded Assignment #1

To be completed before the next lecture on Tues. Send exercise solutions via email to the TA, Sivaram Burra, at burra@cis.udel.edu.
Reading:
Horstmann & Cornell, chap. 3
Exercises:

1. (a) Copy the file example-progs/helloworld/HelloWorld.java to one of your directories.

(b) Alter the class HelloWorld to create a class Delaware that is an applet that prints the word "Delaware" in gold (or yellow) letters on an oval that has a blue background. Make the border around the oval black.

The solution directory .

(c) The third part of this exercise is designed to help you start becoming familiar with using the Java documentation - either the online documentation or Java in a Nutshell. Put the answers to the questions below in the comments of your program. Give a function prototype for the method Graphics.drawOval(). To which class does the method belong. What is the difference between the methods drawOval and fillOval().

To reach the online documentation, click the "Java 2 API" button at the top of a page. To find answers to questions like the ones above, use the index when you get to the Java 2 API web site. To use Java in a Nutshell, look in the index for the method names.

2. (a) What does the word "deprecated" mean in the Java context. Use either the Java Glossary or your textbook to answer this question. (b)What is the total number of public constructors in the class String? How many are deprecated?

Homework Grading and Lateness Policies

Homework assignments will normally be graded on a scale of 0-10. Homework that is n days late will be penalized 1 + 2 + ... + n points. So
One day late =   penalty of 1 point
Two days late =   penalty of 3 points
Three days late =   penalty of 6 points
Four or more days late =   no credit.

The clock ticks forward one day each day at 12:30PM, the beginning of class hour.

Today's Lecture Topics

  1. Overview of the Java compile/execute cycle. (Slide courtesy of JavaOne: Sun's 1997 Worldwide Java Development Conference)

  2. Compiling and executing an application. Make sure that you know how to do this by compiling and executing the program in the file CISC370HOME/CoreJavaBook/v1ch2/Welcome/Welcome.java We will demonstrate this a number times when we discuss the random sentence generating examples later in the lecture.

  3. A second example, "Hello World," Java style. See the directory example-progs/helloWorld/HelloWorld.java .

  4. Java Strings: Generating random sentences - another Java application.

    First, a non-object-oriented C++ program for generating random sentences . This program is in the file $CISC370HOME/example-progs/randomSentences/c++/RandomSentences.cc.

    Now a Java random sentence generator that mimics the C++ program and is not object-oriented. This program is in the file $CISC370HOME/example-progs/randomSentences/java/RandomSentences.java .

    Thirdly, a Java object-oriented version of the program that uses the newly defined class RandomSentMachine that implements a random sentence generating machine that has a public interface similar to the interface for the "standard" class java.util.Random. This program is in two files. The file $CISC370HOME/example-progs/randomSentences/java/RandomSentMachine.java contains the definition of the class RandomSentMachine that defines an object (or machine) that generates random sentences. The second file, $CISC370HOME/example-progs/randomSentences/java/RSMachineTester.java contains a main method that implements a simple driver for testing the RandSentMachine class.

    What makes this code object-oriented and the others non-OO? The focus in object-oriented programming is on the nouns in the problem description whereas in the older programming style the emphasis was on the verbs.

    So in the OO version, we think of implementing a machine for generating random sentences. If we think of this machine as a physical object (and this is often a good way to think about OO design), we want to have a "button" on it that when depressed causes the machine to generate another random sentence. To make this machine, we realize that we need a random number generating machine. So we order a "Sentium" random number chip from "Outel" that we use as a component inside our machine. :)

    When we implement our "machine" as a class, the components like the Sentium chip become instance variables (RNMachine in our RandomSentMachine class) that are assigned an object of the required type (a Random object in this case). "Buttons" are a part of the public interface of the object and are implemented as public methods (if the class had a graphics user interface, we might have such a button). We call our method nextSent() so that it will be analogous to the nextInt()( method in the class java.util.Random. A fancier "machine" for generating random sentences would have more "buttons" (public methods).

    All of these programs are in the directory CISC370HOME/example-progs/randomSentences/ .

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Corrections, suggestions and comments to Bob Caviness

Copyright 2000 B. F. Caviness