Using Loops with Arrays

How to iterate through an array using loops?

Arrays and loops are frequently used in tandem. When dealing with a large array containing 100 or even 1000 elements, manually working with and extracting each element would be impractical. Just imagine how time-consuming it would be to manually fill such an array...

To achieve such tasks, we'll employ loops. In the previous section, we observed that we initially assigned the variable i a value of 0 in the for loop, and array indexing also starts at 0.

Let's say we have a task to display all the elements of an array of type char with a length of 10. Let's examine a code fragment that accomplishes this task:

Main

package com.example;

public class Main {

public static void main(String[] args) {

// Initializing a char array

char[] charArray = {'c', 'o', 'd', 'e', 'f', 'i', 'n', 'i', 't', 'y'};

// Printing the array using a for-loop

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

System.out.print(charArray[i]);

}


              12345678910111213
            
package com.example;

public class Main {
    public static void main(String[] args) {
        // Initializing a char array
        char[] charArray = {'c', 'o', 'd', 'e', 'f', 'i', 'n', 'i', 't', 'y'};
        
        // Printing the array using a for-loop
        for (int i = 0; i < charArray.length; i++) {
            System.out.print(charArray[i]);
        }
    }
}

Let's take a closer look at how the loop iterates over an array:

Main

package com.example;

public class Main {

public static void main(String[] args) {

// Initializing the char array

char[] charArray = {'c', 'o', 'd', 'e', 'f', 'i', 'n', 'i', 't', 'y'};

// Printing the array using a for-loop

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

System.out.println("Now variable i = " + i + ", and value of charArray[" + i + "] = " + charArray[i] + ";");

// The value of `i` increments with each loop iteration

}


              1234567891011121314
            
package com.example;

public class Main {
    public static void main(String[] args) {
        // Initializing the char array
        char[] charArray = {'c', 'o', 'd', 'e', 'f', 'i', 'n', 'i', 't', 'y'};
        
        // Printing the array using a for-loop
        for (int i = 0; i < charArray.length; i++) {
            System.out.println("Now variable i = " + i + ", and value of charArray[" + i + "] = " + charArray[i] + ";");
         // The value of `i` increments with each loop iteration
        }
    }
}

Task

Swipe to start coding

We have an array with the hours worked by an employee over a number of days. You need to calculate the average number of hours per day and provide feedback based on the result.

Create a method called calculateAverage(int[] workHours) that returns a double.
Inside this method:
- Determine the length of the array and store it in a variable (e.g., sizeMassive).
- Use a for loop to iterate over each element of the array.
- Accumulate the total number of hours into a variable totalHours.
- After the loop, compute the average by dividing totalHours by the size of the array, casted to double.

Solution

solution

package com.example;

public class Main {

public static double calculateAverage(int[] workHours) {

int sizeMassive = workHours.length;

int totalHours = 0;

for (int i = 0; i < sizeMassive; i++) {

totalHours += workHours[i];

}

return totalHours / (double) sizeMassive;

}

public static void main(String[] args) {

int[] workHours = {7, 8, 6, 9, 7, 7, 8, 7, 6, 9};

double average = calculateAverage(workHours);

if (average < 8) {

System.out.println("Penalty: employee worked " + average + " hours on average.");

} else {

System.out.println("Good job! Employee worked " + average + " on average.");

}

Everything was clear?

Thanks for your feedback!

Section 4. Chapter 2

package com.example;

public class Main {

public static double calculateAverage(int[] workHours) {

int sizeMassive = ___;

int totalHours = 0;

for (___) {

totalHours += ___;

}

return ___;

}

public static void main(String[] args) {

int[] workHours = {7, 8, 6, 9, 7, 7, 8, 7, 6, 9};

double average = calculateAverage(workHours);

if (average < 8) {

System.out.println("Penalty: employee worked " + average + " hours on average.");

} else {

System.out.println("Good job! Employee worked " + average + " on average.");

}