Assignment 5: Can’t spell functions without fun

Due Thursday, October 20, before midnight

The goals of this assignment are:

  • Write programs containing multiple functions

  • Work with loops, conditionals, and variables

Menu

credit: Jeffrey Knerr

In the file called Menu.java implement a static function called menu that has the following function signature

// Given a list of Strings (user options), displays the strings in a numerical
//   menu and asks the user for their choice
// param opts (String[]): list of String representing all options
// return (int): the id of the option chosen by the user. id is in range [0, opts.length-1].
public static int menu(String[] opts)

This function should work with any list of string options. For example, if the list of options is ["yes","no"], your function will display a simple menu with two options:

 1. yes
 2. no

and then ask the user to choose one of the options (1 or 2). Similarly, if the list of options is ["sit","stay","bark"], your function will display:

 1. sit
 2. stay
 3. bark

Your function needs to work for any size String[] array (2 options, 5 options, 27 options, etc), and should return an integer in the range [0, opts.length].

Furthermore, your function needs to check that the user entered a valid number. You should re-use your IsInteger function and use it to test whether the user provides a value within the valid range.

Once you know you have an integer, make sure the user enters a number from the displayed menu, asking again if they enter a number too high or too low. Once the function gets a valid number, it should return that number as an integer to main().

Helpful Code Examples

Here’s an example of the full program, with the user entering invalid integers at first. Note how the function continues to ask again and again until the user enters a valid choice (hint: use a while loop for that part).

$ javac Menu.java CheckInput.java
$ java Menu
 1. yes
 2. no

your choice --> 0
please enter a valid choice!!!

your choice --> zebra
please enter a positive integer...

your choice --> -1
please enter a positive integer...

your choice --> 99
please enter a valid choice!!!

your choice --> 1
You chose: 1

In Menu.java, use the following simple main() function to test your menu function.

public static void main(String[] args) {
  String[] opts = {"yes","no"};
  int choice = menu(opts);
  System.out.println("You chose: " + choice);
}

Once your function is working, please add at least one additional option ("maybe"?) to opts in main() to make sure your function works with more than two options.

$ java Menu
 1. yes
 2. no
 3. maybe

your choice -->

Patterns

credit: Jeffrey Knerr

This program will use various functions to draw patterns in the terminal window. We’ll write and test each function as we go, then use the menu(opts) function from above to allow the user to pick which function to run.

Start by writing and testing each of the following functions (in Patterns.java).

Block

Implement the block function according to the following specification

// Draw an n by n block to the console
// param n (int): the size of the block
// param ch (char): the character to fill the block
public static void block(int n, char ch)

This function takes a number (n) and a character (ch) and prints a block of nxn characters. For example, calling block(5,'X') would display this to the terminal:

XXXXX
XXXXX
XXXXX
XXXXX
XXXXX

and calling block(10,'Q') would display a 10x10 block of Qs.

In Patterns.java add your block(n,ch) function and call it with a simple main() function to test that it works:

public static void main(String[] args) {
  int n = Integer.parseInt(args[0]);
  block(n,'X');
}

Triangle

Implement the triangle function according to the following specification

// Draw a right triangle with height n to the console
// param n (int): the height of the triangle
// param ch (char): the character to fill the shape
public static void triangle(int n, char ch)

Similar to the block() function, this function takes a number and a character, and displays a triangle pattern. Calling triangle(7,'Y') would display this:

Y
YY
YYY
YYYY
YYYYY
YYYYYY
YYYYYYY

In Patterns.java add your void triangle(int n,char ch) function and call it from main() to test that it works.

Reverse

Implement the reverse function according to the following specification

// Draw a reverse right triangle with height n to the console
// param n (int): the height of the triangle
// param ch (char): the character to fill the shape
public static void reverse(int n, char ch)

Similar to the triangle() function, this function takes a number and a character, and displays a reverse triangle pattern. Calling reverse(5,'P') would display this:

    P
   PP
  PPP
 PPPP
PPPPP

In Patterns.java add your void reverse(int n,char ch) function and call it from main() to test that it works.

Diamond

Implement the diamond function according to the following specification

// Draw a diamond height 2*n to the console
// param n (int): the half-height of the diamond
// param ch (char): the character to fill the shape
public static void diamond(int n, char ch)

Last one! Calling diamond(5,'J') would display this:

    JJ
   JJJJ
  JJJJJJ
 JJJJJJJJ
JJJJJJJJJJ
JJJJJJJJJJ
 JJJJJJJJ
  JJJJJJ
   JJJJ
    JJ

Notice that, for the above example, the first 5 lines just look like the output of reverse() and triangle() put together. You can’t call them together to make those 5 lines, but you can use code similar to what’s in those functions to display the first 5 lines. Then the bottom 5 lines can be done with a separate for loop.

In Patterns.java add your void diamond(int n, char ch) function and call it from main() to test that it works.

Menu

Finally, call your int menu(String[] opts) function from the previous program to Patterns.java. Then rewrite main() to allow the user to pick which pattern to draw, or to quit the program. If the user decides to display a pattern, pick the number (n) and the character (ch) using the random library. Make the number from 5-15, and the character an uppercase letter from A-G.

To compute a random number, choose an integer from 0 to 25 inclusive and then add it to the character a.

Your final program should allow the user to continue selecting patterns to draw, until they select the "quit" option.

Here’s one possible run of the final program:

$ javac Patterns.java Menu.java CheckInput.java
$ java Patterns
 1. block
 2. triangle
 3. reverse
 4. diamond
 5. quit

your choice --> 1
CCCCCCCCCC
CCCCCCCCCC
CCCCCCCCCC
CCCCCCCCCC
CCCCCCCCCC
CCCCCCCCCC
CCCCCCCCCC
CCCCCCCCCC
CCCCCCCCCC
CCCCCCCCCC

 1. block
 2. triangle
 3. reverse
 4. diamond
 5. quit

your choice --> 2
F
FF
FFF
FFFF
FFFFF
FFFFFF
FFFFFFF
FFFFFFFF
FFFFFFFFF
FFFFFFFFFF
FFFFFFFFFFF

 1. block
 2. triangle
 3. reverse
 4. diamond
 5. quit

your choice --> 1
BBBBBB
BBBBBB
BBBBBB
BBBBBB
BBBBBB
BBBBBB

 1. block
 2. triangle
 3. reverse
 4. diamond
 5. quit

your choice --> 1
GGGGGGGGG
GGGGGGGGG
GGGGGGGGG
GGGGGGGGG
GGGGGGGGG
GGGGGGGGG
GGGGGGGGG
GGGGGGGGG
GGGGGGGGG

 1. block
 2. triangle
 3. reverse
 4. diamond
 5. quit

your choice --> 3
              A
             AA
            AAA
           AAAA
          AAAAA
         AAAAAA
        AAAAAAA
       AAAAAAAA
      AAAAAAAAA
     AAAAAAAAAA
    AAAAAAAAAAA
   AAAAAAAAAAAA
  AAAAAAAAAAAAA
 AAAAAAAAAAAAAA
AAAAAAAAAAAAAAA

 1. block
 2. triangle
 3. reverse
 4. diamond
 5. quit

your choice --> 5
You can call javac *.java to compile all the java files in your current directory.

What to hand-in

  1. The programs, CheckInput.java, Menu.java and Patterns.java

  2. Make sure your program has a header containing your name, date, and purpose of the program

  3. A brief write-up containing your name, assignment number, and a few sentences about how long you spent on the assignment and any interesting bugs you solved. Be sure to describe the unique pattern you implemented!

How to hand-in

  1. Copy your files to your dropbox, into the folder called A05.