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Java Basics
course content

Kurssisisältö

Java Basics

Java Basics

1. Getting Started
Backend DevelopmentRole of Java in the Backend Java Advantages Memory Types In Java Java's SyntaxYour First ProgramComments
2. Basic Types and Operations
Primitive Data TypesChallenge: Primitive TypesMathematical Operations on charMathematical Operations in JavaIf-Else StatementSwitch-Case StatementNew Task StructureChallenge: Weekday Switch
3. Loops
Introduction to LoopsWhile-LoopDo-While LoopChallenge: Building a Server Retry MechanismFor-Loop Increment and DecrementInfinite LoopChallenge: Filtering Numbers in a Loop
4. Arrays
What is Array?Using Loops with ArraysIndex Out Of BoundsTwo-Dimentional ArrayIteration In Two-Dimensional ArrayFor-Each Loop
5. String
What Is String? Basic Methods In StringPractical Applications of String MethodsChallenge: Filter Failure MessagesNullPointerException StringBuilderString Pool, Method Equals() Summary

book
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:

java

Main

copy

              
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:

java

Main

copy

              
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
        }
    }
}
Tehtävä

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.

  1. Create a method called calculateAverage(int[] workHours) that returns a double.
  2. 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.

Ratkaisu

java

solution

Switch to desktopVaihda työpöytään todellista harjoitusta vartenJatka siitä, missä olet käyttämällä jotakin alla olevista vaihtoehdoista
Oliko kaikki selvää?

Miten voimme parantaa sitä?

Kiitos palautteestasi!

Osio 4. Luku 2
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book
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:

java

Main

copy

              
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:

java

Main

copy

              
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
        }
    }
}
Tehtävä

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.

  1. Create a method called calculateAverage(int[] workHours) that returns a double.
  2. 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.

Ratkaisu

java

solution

Switch to desktopVaihda työpöytään todellista harjoitusta vartenJatka siitä, missä olet käyttämällä jotakin alla olevista vaihtoehdoista
Oliko kaikki selvää?

Miten voimme parantaa sitä?

Kiitos palautteestasi!

Osio 4. Luku 2
Switch to desktopVaihda työpöytään todellista harjoitusta vartenJatka siitä, missä olet käyttämällä jotakin alla olevista vaihtoehdoista
Pahoittelemme, että jotain meni pieleen. Mitä tapahtui?
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