Week 3 Class Exercises

Exercise 1: if

Write a program that asks the user to enter a three letter word. The program should indicate whether the letters in the word are in alphabetical order, reverse alphabetical order, or neither. Sample interaction should look like this:

Enter three letters: aim
The three letters entered are in alphabetical order.

Enter three letters: tub
The three letters entered are in reverse alphabetical order.

Enter three letters: bye
The three letters entered are not in order.

Exercise 2: switch

Suppose you are making a game that needs to control a character on the screen. The following key mappings should be used: h - left, j - down, k - up, l - right. Write a program that accepts a character and prints the appropriate direction. Sample interaction should look like this:

j
down

k
up

h
left

Exercise 3: Rewrite for loop as while loop

Rewrite the following for loop as a while loop:

for(int i=1; i<10; i=i+1) {
  System.out.println(i + "^2 = " + i*i);
}

Exercise 4: Loops

Write a program that asks the user to enter a word. The program should indicate whether the letters in the word are in alphabetical order, reverse alphabetical order, or neither. Sample interaction should look like this:

Enter a word: abhors
The letters entered are in alphabetical order.

Enter a word: soon
The letters entered are in reverse alphabetical order.

Enter a word: typical
The letters entered are not in order.

Exercise 5: do while loop

Write a program that shows a pop-up box asking the user to enter something. If the user clicks OK without entering anything, the program should ask the user again (repeatedly, until the user enters something). The program should then end. It is okay for the program to crash if the user clicks Cancel. Optionally, you could modify your program to end if the user clicks Cancel (hint: if the String returned from the showInputDialog() call is null).

Exercise 6: Loops

Ask the user to enter two integer values: height and width. Your program should then generate a box of *s that is height tall and width wide. Sample interaction may look like this:

Please enter the height: 3
Please enter the width: 5

*****
*****
*****

Exercise 7: Loops

Ask the user to enter a name and print all of the letters in the name, one per line. Include line numbers for the lines. Sample interaction may look like this:

Enter a name: Chris
Letters:
1. C
2. h
3. r
4. i
5. s

Exercise 8: Loops

Ask the user to enter as many positive integers as the user wants followed by a non-positive integer. The program should then display the sum of all positive values that are divisible by 3. Sample interaction may look like this:

Enter a bunch of positive integers followed by a non-positive integer:
1 2 3 4 5 6 7 8 9 10 11 18 0

Answer: 36

Exercise 9: Loops

Suppose you are making a game that needs to control a character on the screen. The following key mappings should be used: h - left, j - down, k - up, l - right. Write a program that accepts a string of characters and generates a sequence of moves. Characters other than the directional characters specified earlier should be ignored. Sample interaction should look like this:

jjlllk
down
down
right
right
right
up

Exercise 10: Loops

Rewrite the program in the previous exercise so that the output matches the sample below.

jjlllk
2 down
3 right
1 up