COMP 110-003 Fall 2008

Description

In-class exercise 1

Download Lab2InClass1.java and try to compile it in jGRASP.

1. You will get a compiler error. What is the error? Why did you get this error?

2. Use type casting to fix the code. Compile the code again. Run the code and input the value 20. What is the output of the program?

3. Run the code again, and this time input the value 2000. What is the output of the program? Why? Hint: look at Display 2.2 on p. 53 (4th edition) or Figure 2.1 on p. 48 (5th edition).

In-class exercise 2

Download Lab2InClass2.java and compile it in jGRASP.

1. Run the program, and enter 3 as the input. Why does the output say 0.00%?

2. Use type casting to fix the code.

Part 1 (7 points)

Characters are stored as numbers in a computer. Each character has a unique Unicode character code. Appendix 3 (4th edition) and Appendix 7 (5th edition) have a subset of the Unicode character set. Download UnicodeFun.java (don't forget to add the appropriate header!). Compile the program and run it. You should see:

Hello world!

Note that the " world!" part of the output is constructed using integers that are type cast as characters. Change the program so that it instead says:

Hello yourfullname!

where yourfullname is, of course, your full name. For example, for me, the output would be:

Hello Luv Kohli!

Everything that comes after "Hello" must be constructed using integers that are type cast as characters. Yes, I realize that some people's names are longer than other names, but it will be so exciting to see your name printed using type casting that it won't matter! :-)

Part 2 (15 points)

Download the skeleton program StringFun.java. Compile and run the program in jGRASP. (Don't forget to add the appropriate header!)

For this part of the lab you will modify the code StringFun.java to prompt the user for a string (of characters) and output information about the string as well as manipulate the input string. You will be referencing pages 79-84 (4th edition) or 75-80 (5th edition) of your textbook.

• The program prompts the user to input a string with this line of code:

  String inputString = JOptionPane.showInputDialog("Please enter a string:");

  Your input string will be stored in the variable inputString.

• Manipulate the string stored in inputString. For each step, display a new dialog box using:

  JOptionPane.showMessageDialog(null, your output goes here);

  There is already one example of this in the program that outputs the length of your string. Manipulate the string and display the resulting string as follows:

• Convert inputString to all uppercase letters
• Print out the characters at positions 0 and 5 (assume the user input a string with more than 6 characters)
• Display the substring starting at position 0 and ending at position 5
• Display the inputString without the first word (assume the user input a string with multiple words separated by spaces).
  (Hint: find the index of the first space in the string. Then display the substring starting at the next index past the first space.)

Additional Questions (3 points)

• What was the most helpful part of this lab? the least helpful?
• Has any part of lecture been confusing that you would like covered again? What?

Grading

• 7 points Part 1
• 15 point Part 2, consisting of:
• 3 points Declaring variables and displaying dialog boxes
• 12 points String manipulation
• 3 points Additional Questions

How to hand in the assignment

• A file named yourlastname_lab2.txt (or .doc), where yourlastname is your last name, that provides answers to the Additional Questions. Make sure the file has the appropriate header.
• A file named yourlastname_lab2.jar, where yourlastname is your last name. The .jar file should include UnicodeFun.java and StringFun.java. Your java files should have the appropriate header. Follow these instructions to create yourlastname_lab2.jar.
• Attach yourlastname_lab2.txt (or .doc) and yourlastname_lab2.jar to an email with subject COMP110 Lab2 yourlastname, and send me the email by the deadline.
• If you do not follow these instructions you will not get credit for the lab. Please let me know if you are having any problems with the assignment submission process.