Chapter 16 Exercises

Exercise 1. Traverse an array of integers and print each number on a new line.

Solution:

public class Main {
    public static void main(String[] args) {

        int[] numbers = {1, 2, 3, 4, 5};

        for (int number : numbers) {
            System.out.println(number);
        }

    }
}

Exercise 2. Traverse a String array and print each string on a new line.

Solution:

public class Main {
    public static void main(String[] args) {

        String[] words = {"Hello", "World", "Java", "Programming"};

        for (String word : words) {
            System.out.println(word);
        }

    }
}

Exercise 3. Add all elements of an integer array and print the result.

Solution:

public class Main {
    public static void main(String[] args) {

        int[] numbers = {1, 2, 3, 4, 5};
        int sum = 0;

        for (int number : numbers) {

            sum += number;

        }

        System.out.println("Sum: " + sum);

    }
}

Exercise 4. Find the maximum value in an integer array and print the result.

Solution:

public class Main {
    public static void main(String[] args) {

        int[] numbers = {1, 2, 3, 4, 5};

        int max = numbers[0];
        for (int number : numbers) {

            if (number > max) {
                max = number;
            }

        }

        System.out.println("Maximum: " + max);

    }
}

Exercise 5. Count how many times a specific number appears in an integer array.

Solution:

public class Main {

    public static void main(String[] args) {

        int[] numbers = {1, 2, 3, 2, 4, 2, 5};
        int numberToFind = 2;
        int counter = 0;
        for (int number : numbers) {

            if (number == numberToFind) {
                counter++;
            }

        }

        System.out.println("The number " + numberToFind + " appears " + counter + " times.");

    }
}

Exercise 6. Print the positions of a specific number in an integer array.

Solution:

public class Main {
    public static void main(String[] args) {

        int[] numbers = {1, 2, 3, 2, 4, 2, 5};
        int numberToFind = 2;


        for (int i = 0; i < numbers.length; i++) {

            if (numbers[i] == numberToFind) {

                System.out.println("The number " + numberToFind + " is at position " + i);

            }

        }
    }
}

Exercise 7: Create an array of integers and calculate the average of its elements.

Solution:

public class Main {
    public static void main(String[] args) {

        int[] numbers = {1, 2, 3, 4, 5};
        int sum = 0;

        for (int number : numbers) {

            sum += number;

        }

        double average = (double) sum / numbers.length;
        System.out.println("Average: " + average);

    }

}

Exercise 8. Traverse a string array and convert each string to uppercase, then print them.

Solution:

public class Main {
    public static void main(String[] args) {

        String[] words = {"hello", "world", "java", "programming"};

        for (String word : words) {
            System.out.println(word.toUpperCase());

        }
    }
}

As we have seen, to convert text to uppercase in Java, we use the toUpperCase() method from the String class. This method takes a text string and returns a new string with all letters converted to uppercase. Here I explain how to do it in a simple way. Let’s look at another simple example:

String text = “hello world”;

String textInUppercase = text.toUpperCase();

System.out.println(textInUppercase);

Exercise 9. Traverse an array of integers and multiply each element by 2, printing the results.

Solution:

public class Main {
    public static void main(String[] args) {

        int[] numbers = {1, 2, 3, 4, 5};

        for (int number : numbers) {
            System.out.println(number * 2);
        }

    }	
}

Exercise 10. Traverse a String array and print only even-numbered elements.

Solución:

public class Main {
    public static void main(String[] args) {

        int[] numbers = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

        int evenCounter = 0;

        for (int number : numbers) {
            if (number % 2 == 0) {
                evenCounter++;
            }
        }
        
        System.out.println("Number of even elements: " + evenCounter);

      }
}