Lab 10 In-Class: More Loops

A Menu-Driven Program Using a Do Loop

1. Save Account.java to your directory.

2. The file ATM.java contains a skeleton of the program described above. Complete the program as follows (as indicated by the comments in the program):
   1. Declare and instantiate an Account object with the information read in.
   2. Add a do...while loop that executes until the user chooses to quit. The loop should print out a menu of options in the following format:

               Options:
               1. Deposit
               2. Withdraw
               3. Check the balance
               4. Quit
      
               Enter your choice (1,2,3, or 4): 
      

   3. Then read in the user's choice (in the choice variable already declared) and do what the user requests (which requires using the appropriate method from the Account class). Note that if the user chooses deposit or withdraw, the program must ask for and read in the amount. Also, if the user types in an incorrect choice (such as a 6) the program should print a message telling the user to try again.

3. Thoroughly test your program.

4. Print ATM.java to turn in.

For Loops - Hot Streaks

1. Create a coin object.
2. Inside the loop, use the flip method to flip the coin, the toString method (implicitly -- just print the coin object, and it will call the toString method automatically) to print the results of the flip, and the isHeads method to see if the result was HEADS.
3. To keep track of the current run length (the number of times in a row that the coin was HEADS), note that if the coin is HEADS on this flip, the current run is one longer than it was; if it's not HEADS, then the counter starts over. Be sure to update the maxRun variable as necessary.
4. While you're checking for HEADS, if it's HEADS also print the number it is in the current run. For example, your output might start like this, indicating a longest run (so far) of 4:

   Heads 1
   Heads 2
   Tails
   Tails
   Tails
   Heads 1
   Heads 2
   Heads 3
   Heads 4
   Tails
   Heads 1
   ...
   

   You'll have to work a little on the formatting to get this to come out right (think about where you'll use print and where you'll use println).

5. After the loop, print the length of the longest run (clearly labeled, of course).

6. Print Runs.java to hand in.

Processing Strings & Nested Loops

1. Add declarations for any additional variables you need and initialize them as appropriate.
2. Change the phrase read in to all lower case for easier processing (so you don't have to test for both upper and lower case vowels).
3. Write a for loop to go through the phrase character by character. In the body of the for loop you need to determine if the current character is a letter. If it is you need to count it and then see if it is a vowel. There are several ways to determine if a character is a letter including different ways of comparing characters. However, another way is to use the isLetter method from the Character class. The signature of the method is as follows:

         public static boolean isLetter(char c)
   

   Recall that a static method is called using the class name. Hence, a call would have the form

          Character.isLetter(ch)
   

   where ch is a variable of type char. Since a boolean is returned the above call should be placed in an appropriate place for a boolean such as an if.

4. After the loop print out the number of vowels and the total number of letters, appropriately labeled.

5. Also compute and print the percentage of letters that are vowels. Use a percent formatter object from the NumberFormat class to print the percent. To do this you need to do the following (see pages 131-132 for an example).
   • Add an import statement to import java.text.NumberFormat.
   • Just before you print, get a format object (named fmt for example) as follows:

           NumberFormat fmt = NumberFormat.getPercentInstance();
     

   • Then, in your print statement use the format method to print the percent (note: the formatter multiplies by 100 for you):

      System.out.println ("Percentage of vowels: " + fmt.format(whatever));
     

6. [READ ALL BEFORE DOING ANYTHING!!] It would be nice to have the program let the user keep entering phrases rather than having to restart the program every time. To do this we need another loop surrounding the current code. That is, the current loop will be nested inside the new loop. Add an outer while loop that will continue to execute as long as the user does NOT enter Q or q for the phrase. Note that this makes the outer loop a sentinel controlled loop -- the program is processing phrases and a special value Q will stop it. The outline of the program is as follows:

        read in the first phrase
   
        while the phrase is neither "Q" nor "q"
        {
          initialize the counters etc. to set up the for loop
   
          for loop to count letters and vowels in the phrase
   
          print the number of vowels & letters and percentage of vowels
        
          read in the next phrase or "Q" to quit
        }
   
   

   Note that all you need to do is add the sentinel controlled while loop around the code you already have. Be sure the code to initialize the counters is inside the while loop (you start the counters over for each phrase).

   Be sure to format your code after adding the surrounding loop (SHIFT-CTRL-F) so it is properly indented.

Test your program thoroughly (enter more than one phrase!!!) then print the final version.

Reading Data from a File

       Scanner scan = new Scanner (System.in);

       Scanner fileScan1 = new Scanner (new File ("myFile.txt"));

       // assume fileName is a String variable that already has a value
       Scanner fileScan2 = new Scanner (new File (fileName));

       Scanner fileScan1 = new Scanner (new File ("lab10/myFile.txt"));

       // assume fileName is a String variable that already has a value
       Scanner fileScan2 = new Scanner (new File ("lab10/" + fileName));

Do the following:

1. Download the Java program and the two input files to your lab 10 subdirectory (right click on the link and choose Save Link As). Open the Java program and note the following:
   • Note that the program imports java.io.* which is the Java Class Library package that supports reading from a file.
   • Note that the header of the main method includes the clause "throws IOException" - this is needed in case there is a problem finding or opening the input file.
   • Note where the program instantiates the fileScan variable. It associates the variable with the grades1.txt input file.
   • Note the while loop - it uses fileScan.hasNext() as the loop control. This will be true if there is something left in the file to read and false otherwise.
   • In the body of the loop the fileScan object is used to read information about one student - the integer followed by the String (note that the next method is used so the String read will be all characters up to white space (so the name can't contain spaces - for example, only the Mary part of "Mary Sue" would be read).
   • The only "processing" of the data inside the loop is to print out the information read in, then to count each student (which also counts the number of lines in the file) and to count the students with passing grades (at least 60).

2. Open up grades1.txt to see what the data file looks like. You will see several lines with a number (the grade) followed by a String (the name).

3. Run FileExample.java to see how it works.

4. Note that currently the program only works for a file named grades1.txt. Modify the program so the file name is read in. A Scanner object is already instantiated to read from System.in and a String variable for the file name is already there. You need to:
   1. Prompt for and read in the file name.
   2. Change the instantiation of fileScan so it associates the Scanner object with the file just read in.

5. Run the program and type in grades2.txt for the file name. How many students are in that file? Would you want to type all that in rather than read from a file?

6. Read the whole description of the following problem before doing anything!

   The file nflStats.txt contains some statistics about how some of the NFL quarterbacks did in a recent week of play. Specifically, the file contains the name of the quarterback, the number of times he tried to pass the football and the outcome (in yards) of each pass attempt (note: an outcome of 0 means that the pass was incomplete). The file is organized as follows:

   
   QUARTERBACK_NAME
   NUMBER_OF_PASS_ATTEMPTS
   YARDAGE_1 YARDAGE_2 YARDAGE_3 ... YARDAGE_N
   
   

   Here's a simple example file:

   
       Montana
       13
       12 0 35 23 0 0 8 57 0 14 27 21 0
       Jones
       7
       0 0 0 13 0 67 8
   

   Your job is to write a program, named FootballStats.java, that reads the file and uses the data to compute some aggregate statistics. For each quartback, you should print a nicely formatted message that contains:
   • Quarterback Name
   • Number of Pass Attempts
   • Number of Complete passes
   • Total Yardage
   • Yards per Attempt
   • Yards per Complete Pass

   Moreover, we are interested in identifying the "Best" Quarterback performance. After all the data has been read and processed, your program should print out a message that contains the name of the quarterback that had a) the largest total yards, b) the highest yards per attempt and c) the highest yards per complete pass.

   To accomplish this, you need to do the following for each player:

   • Read in the player's name and number of passes attempted.
   • Read in and process the information about each pass attempt made by the player.

   Clearly you need a nested loop.

   • The inner loop is responsible for reading the information about each pass attempt made by the player. You should process the data by keeping a running total and by counting the number of complete passes.

   • Each iteration of the outer loop will deal with one player - it will read in the information about a single player and compute his statistics.

   • You will also need to compare performance of the quarterbacks to see who is best in each of the three categories (total yards, most yards per attempted pass, most yards per completed pass).

   Plan your program before starting it! You should not try to do everything at once - devise a strategy to complete and test the program in steps (the last exercise may give you a hint about a good strategy for writing a program with a nested loop).

7. Print the completed program.

Hand in:

• Your four printouts: ATM.java, Runs.java, FootballStats.java, and Vowels.java.
• Tar your lab10 directory and e-mail it to your instructor with cpsc120 lab10 in the subject line.