Course Content

Java Basics

1. Getting Started

Backend Development Role of Java in the Backend Java Advantages Memory Types In Java Java's Syntax Your First Program Comments

2. Basic Types and Operations

Primitive Data Types Challenge: Primitive Types Mathematical Operations on char Mathematical Operations in Java If-Else Statement Switch-Case Statement New Task Structure Challenge: Weekday Switch

3. Loops

Introduction to Loops While-Loop Do-While Loop Challenge: Building a Server Retry Mechanism For-Loop Increment and Decrement Infinite Loop Challenge: Filtering Numbers in a Loop

4. Arrays

What is Array?Using Loops with Arrays Index Out Of Bounds Two-Dimentional Array Iteration In Two-Dimensional Array For-Each Loop

5. String

What Is String? Basic Methods In String Practical Applications of String Methods Challenge: Filter Failure Messages NullPointerException StringBuilder String Pool, Method Equals() Summary

While-Loop

In the previous chapter, you could see that with the help of a loop, we repeated the code 10 times. Now, let's examine the syntax of one of these loops.

while loop

The while loop is the simplest example of a loop in action. This loop will repeatedly execute a code block as long as the condition inside the condition block evaluates to true. Once the condition returns false, the loop execution will stop.

Main


              123
            
while (condition) {
    // code to be executed
}

To remember how this loop works, you can follow a simple rule: While the condition is true, perform the operation. For example, while it's raining, I use an umbrella. As soon as the rain stops, I go without an umbrella.

It's raining - the condition
I use an umbrella - the code executed inside the loop
The rain has stopped - the compiler exits the loop and stops executing the code inside the loop.

Now, let's take a look at a more detailed explanation of how the while loop works:

The condition is evaluated before each iteration. If the condition is true, the code block inside the loop is executed. If the condition is false, the loop is terminated, and the program continues with the next statement after the loop;
The code block inside the loop can contain one or more statements. These statements will be executed repeatedly as long as the condition remains true;
It's important to ensure that the condition eventually becomes false, or the loop will run indefinitely, causing an infinite loop.

Here's an example to demonstrate the while loop:

Main


              123456789101112131415
            
package com.example;

public class Main {
    public static void main(String[] args) {
        int a = 0;
        int b = 10;
        while (a != b) {
            a = a + 1;
            System.out.println("a has value: " + a);
            b = b - 1;
            System.out.println("b has value: " + b);
        }
        System.out.println("Is a equals to b: " + (a == b));
    }
}

In this code, we have two variables of type int. In our loop, we set a condition that reads as follows: as long as the value of variable a is not equal to the value of variable b, we increment variable a and decrement variable b. When their values are equal, we terminate the while loop.

Task

Swipe to start coding

Find the sum of a range of numbers from 1 to n.

Create a method called sumFrom1ToN(int n) that returns an int result.
Inside the method, define two variables:
- sum (to store the total).
- current (starting from 1).
Use a while loop to repeat the following steps until current is greater than n:
- Add the value of current to the sum.
- Increment current by 1.
Return the total sum at the end of the loop.

Solution

solution

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Section 3. Chapter 2

While-Loop

In the previous chapter, you could see that with the help of a loop, we repeated the code 10 times. Now, let's examine the syntax of one of these loops.

while loop

Main


              123
            
while (condition) {
    // code to be executed
}

It's raining - the condition
I use an umbrella - the code executed inside the loop
The rain has stopped - the compiler exits the loop and stops executing the code inside the loop.

Now, let's take a look at a more detailed explanation of how the while loop works:

The condition is evaluated before each iteration. If the condition is true, the code block inside the loop is executed. If the condition is false, the loop is terminated, and the program continues with the next statement after the loop;
The code block inside the loop can contain one or more statements. These statements will be executed repeatedly as long as the condition remains true;
It's important to ensure that the condition eventually becomes false, or the loop will run indefinitely, causing an infinite loop.

Here's an example to demonstrate the while loop:

Main


              123456789101112131415
            
package com.example;

public class Main {
    public static void main(String[] args) {
        int a = 0;
        int b = 10;
        while (a != b) {
            a = a + 1;
            System.out.println("a has value: " + a);
            b = b - 1;
            System.out.println("b has value: " + b);
        }
        System.out.println("Is a equals to b: " + (a == b));
    }
}

Task

Swipe to start coding

Find the sum of a range of numbers from 1 to n.

Create a method called sumFrom1ToN(int n) that returns an int result.
Inside the method, define two variables:
- sum (to store the total).
- current (starting from 1).
Use a while loop to repeat the following steps until current is greater than n:
- Add the value of current to the sum.
- Increment current by 1.
Return the total sum at the end of the loop.

Solution

solution

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Everything was clear?

Thanks for your feedback!

Section 3. Chapter 2

Switch to desktop for real-world practiceContinue from where you are using one of the options below