Comp101 Lab 3

Introduction:

In this lab you will continue your java programming experience writing a very simple class with several methods. You will take the part of an applications programmer who is developing a class for another programmer who will build the actual application.

Objectives:

Define a class in java
Define methods in java
Define a constructor
add instance variables to your class.

You will be implementing a class to do some simple string manipulation. Annother application programmer has built a user interface (and isn't it a beauty!?!???) to function as an extreemly simple string manipulating toy program. Your job is to write class that does the string handling according to the specifications provided. Because the user interface is written for you, you must write your class exactly as it is specified.

First copy the start file for this lab to your folder. After you login

cp ~jsantore/Lab3Start.zip .

Remember that that final dot is important for the command, its not punctuation.
unzip the file as usual

unzip Lab3Start.zip

and then cd into the newly created Lab3 directory.

You have only one file this time. Morover, it will not compile until you do at least some of your assignment. When everything does compile and you run the program, you should see a window that looks alot like this:
Lab3 up and running

The behavior that we expect to see is this:

When you type some text into the two text boxes, select one of the radio buttons and press 'Do It'. The result will be displayed on the label next to the Do It button. (the one that says "THIS IS SILLY" in the picture above.) The radio buttons are described below:

Length shows the length of both the left and right text added together.
Combine shows the left text and the right text combined into a single string.
UpCase takes the text from the left text box and makes all of of the text upper case.
Is Same will print They are the same! if the two text boxes have the same text in them and a different message if they are different.
Prof's will display a string that I'm sending to your class.

Specifications of the class that you must write

You need to write a class with the following specifications. Since I've written a class that uses yours, your class name, method names, and Parameter lists must match those that I list below.

The class must be named StringHelper
It must have an instance variable of type String.
The class must have a constructor and that constructor must take one String as its parameter and use that paremeter to initialize the instance variable
The class must have 5 more methods

A Method called lengthOfBothStrings which takes two parameters of type String and returns a value of type int

this method should return the value obtained by adding the lengths of its two parameters

A Method called combineStrings which takes two parameters of type String and returns a value of type String

this method should return the value obtained by concatinating its first parameter and its second parameter together in that order.

A Method called makeBig which takes one parameter of type String and returns a value of type String

this method should return an upcased version of the parameter.

A Method called isSame which takes two parameters of type String and returns a value of type boolean

this method should return return true if the two strings have the same text, otherwise it should return false.

A method called getInstructorsString which takes no explicit parameters and returns a string.

this method must return the value of the instance variable.

Once you have written all of the methods and the property of the StringHelper class correctly and everything compiles and works then you are done.

Most of the work that you will be doing in the methods that you have to write can be done for you by applying methods from the String class. As you know you can find those by searching through the API. But thats still a bit of work as early in your learning as you are so below are a few of the methods from the string class. All of the methods that you need (and one or two extra) to do this lab are found below.

String concat(String str)
Concatenates the specified string to the end of this string.

`boolean`	`endsWith(String suffix)` Tests if this string ends with the specified suffix.
`boolean`	`equals(Object anObject)` Compares this string to the specified object.
`boolean`	`equalsIgnoreCase(String anotherString)` Compares this `String` to another `String`, ignoring case considerations.

`int`	`length()` Returns the length of this string.
`boolean`	`matches(String regex)` Tells whether or not this string matches the given regular expression.

String toUpperCase()
Converts all of the characters in this String to upper case using the rules of the default locale.

Starting up

When you begin, I suggest that you let xemacs help you out a little. Once you are in your Lab3 folder, open the file that you get (the one in which I implemented the Graphical User Interface (GUI)) using xemacs

xemacs Lab3App.java&

You don't need to look at this file closely or understand it since it does many things that you have not yet learned about. Select the file menu and choose the "JDE New" submenu and then choose "class" from that submenu. xemacs will ask you in the for the name of the new java file. (in the small text bar at the bottom of xemacs - see image - note that the text colors might be different for you)
using xemacs and jde to create a new java class file

using xemacs and jde to create a new java class file

Next xemacs will pop up its "file open dialog asking for the file name of the new Java class you are creating
xemacs file open dialog prompting for the java file name

xemacs file open dialog prompting for the java file name

Type in StringHelper.java. You must define your java class in a file with the same name as the class itself (with the .java extension)
You're going to be promted to enter some information about the class as you can see in the image below. Don't bother with a package when prompted, just hit enter.
xemacs prompting for the package for your new java class

xemacs prompting for the package for your new java class

xemacs will now ask you what this class extends. We haven't learned about extending classes so you can simply type enter to default to nothing. The same with the next two questions about what this class implements.

Now you have a simple class outlined for you. It has a constructor (to which you still need to add the correct parameter ) and nothing more. Now add the instance variable, fix the contructor and add the rest of the methods that you need.

Submitting

When you submit this time, add a readme.txt file to your Lab3 folder that you are building. (In xemacs you create a new file by doing <file><open file> and typing in a brand new file name. The readme should contain:

Your name.
A very brief summary of what you did
A list of any problems still in your code or anything that you didn't get done.

Once you have the readme done, cd into your parent folder, zip up the entire Lab3 folder using the -r flag as you have learned in the last two labs, and use the online submission program to submit it to me.

Due Monday Feb 25th at 11:59pm (note holiday weekend and odd schedule between now and then)


`String`	`toUpperCase()` Converts all of the characters in this `String` to upper case using the rules of the default locale.