Challenges

Early on, most students tend to have a lot of trouble with loops. Its also what is quizzed on in a lot of standardized tests.

Because of that there will be a lot of challenges in this section for you to practice. Try to at least do the first ten or so to make sure you have the concept down, but the more the better.

It might take awhile before you feel truly comfortable with this. That is normal.

Remember the rules for this are

• Try to use only the information given up to this point in this book.
• Try not to give up until you've given it a solid attempt

Challenge 1

Write code that outputs every number from 1 to 10.

public class Main {
    public static void main(String[] args) {
        <CODE HERE>
    }
}

Challenge 2

What will this program output when run? Write down your guess and then try running it.

public class Main {
    public static void main(String[] args) {
        int x = 0;
        while (x < 10) {
            System.out.println(x);
            x++;
        }
    }
}

Challenge 3

What will this program output when run? Write down your guess and then try running it.

public class Main {
    public static void main(String[] args) {
        int x = 0;
        while (x <= 10) {
            System.out.println(x);
            x++;
        }
    }
}

Challenge 4

What will this program output when run? Write down your guess and then try running it.

public class Main {
    public static void main(String[] args) {
        int x = 0;
        while (x < 10) {
            if (x % 3 == 0) {
                break;
            }
            System.out.println(x);
            x++;
        }
    }
}

Challenge 5

What will this program output when run? Write down your guess and then try running it.

public class Main {
    
    public static void main(String[] args) {
        int x = 0;
        while (x < 10) {
            if (x % 3 == 0) {
                continue;
            }
            System.out.println(x);
            x++;
        }
    }
}

Challenge 6

What will this program output when run? Write down your guess and then try running it.

public class Main {
    public static void main(String[] args) {
        int x = 1;
        while (x < 10) {
            int y = 2;
            while (y < 5) {
                System.out.println(x * y);
                y++;
            }
            
            x++;
        }
    }
}

Challenge 7

What will this program output when run? Write down your guess and then try running it.

public class Main {
    public static void main(String[] args) {
        int x = 0;
        String scream = "a";
        while (!scream.equals("aaaaaaaa")) {
            scream = scream + "a";
            System.out.println(x);
            System.out.println(scream);
        }
    }
}

Challenge 8

Write code that will output each character of name on its own line.

So for if name is equal to "Bridget", I would expect the following as output.

B
r
i
d
g
e
t

public class Main {
    public static void main(String[] args) {
        // Change this value to test your code.
        String name = "Bridget";

        // <CODE HERE>
    }
}

Challenge 9

Write code that will output each character of name on its own line, starting with the last character and going backwards.

So for if name is equal to "Samantha", I would expect the following as output.

a
h
t
n
a
m
a
S

public class Main {
    public static void main(String[] args) {
        // Change this value to test your code.
        String name = "Samantha";

        // <CODE HERE>
    }
}

Challenge 10

Write code that will take a number and if it is divisible by two, divides it by two. If it is not, multiplies it by three and adds one.

Keep doing this until the number equals one. Output it each time.

If the initial number is 6 you should have this as output.

6
3
10
5
16
8
4
2
1

If the initial number is 15 you should have this as output.

15
46
23
70
35
106
53
160
80
40
20
10
5
16
4
2
1

public class Main {
    public static void main(String[] args) {
        // Change this value to test your code.
        int n = 15;

        // <CODE HERE>
    }
}

Challenge 11

Write code that outputs every third number from 37 to 160.

public class Main {
    public static void main(String[] args) {
        <CODE HERE>
    }
}

Challenge 12

Write code that outputs the number of vowels in name. Treat y as a vowel.

Treat the characters a, A, e, E, i, I, o, O, u, U, y, and Y as vowels.

public class Main {
    public static void main(String[] args) {
        // Change this value to test your code.
        String name = "Damian";

        // <CODE HERE>
    }
}

Challenge 13

Write code that outputs {name} is mostly vowels if the number of vowels in name is greater than the number of consonants. and {name} is mostly consonants if the opposite is true. Output {name} has an equal number of vowels and consonants if the count of both is the same.

Make sure to not treat non-alphabetic characters like ! and ? as consonants.

public class Main {
    public static void main(String[] args) {
        // Change this value to test your code.
        String name = "Messi";

        // <CODE HERE>
    }
}

Challenge 14

Rewrite the following code to not have the shouldBreak variable and instead to use a labeled break.

public class Main {
    public static void main(String[] args) {
        // Don't think too hard about what these numbers mean.
        int x = 3;
        int y = 0;

        boolean shouldBreak = false;
        while (shouldBreak && x < 100) {
            while (y < 100) {
                System.out.println("x is " + x);
                System.out.println("y is " + y);
                x = x * y;
                if (x == 0) {
                    shouldBreak = true;
                    break;
                }
                y++;
            }
        }

        System.out.println("Done");
    }
}