Kursinnehåll

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

Comments

Hiding code in from the compiler

You can hide code from the compiler by commenting out the code.

Code comments are fragments that the compiler will not process.

You can comment out lines of code using the // symbols or enclose a specific fragment of text or code using /* */.

Why do we need comments?

Comments let you write notes to explain what parts of the code do. These notes are ignored by the computer but make the code easier to understand for yourself or others;
Comments can temporarily disable parts of your code. For instance, if you think a specific line is causing an error, you can comment it out (/* code fragment */) to test the program without that line;
Comments can be used to describe how your code works, making it easier to understand later or for others working with your code.

You saw an example of commenting in the previous chapter, where a comment was placed where the code was supposed to go.

Here's another example of how to use comments:

Main


              123456789
            
package com.example;

public class Main {
    public static void main(String[] args) {
        System.out.println("Message 1");
        // System.out.println("Message 2");
	    System.out.println("Message 3");
    }
}

Only the first and third messages will be displayed here because the second part is commented out, so the compiler ignores it.

Now, let's take a look at an example of multi-line code commenting:

Main


              123456789
            
package com.example;

public class Main {
    public static void main(String[] args) {
        /* System.out.println("Message 1");
        System.out.println("Message 2"); */
        System.out.println("Message 3");
    }
}

As you can see, only the third message is displayed in the console because the first and second ones are commented out.

Uppgift

Swipe to start coding

Your task is to identify the error and comment out the code fragment that contains it.

Lösning

solution

Byt till skrivbordet för praktisk övningFortsätt där du är med ett av alternativen nedan

Var allt tydligt?

Tack för dina kommentarer!

Avsnitt 1. Kapitel 7

Comments

Hiding code in from the compiler

You can hide code from the compiler by commenting out the code.

Code comments are fragments that the compiler will not process.

You can comment out lines of code using the // symbols or enclose a specific fragment of text or code using /* */.

Why do we need comments?

Comments let you write notes to explain what parts of the code do. These notes are ignored by the computer but make the code easier to understand for yourself or others;
Comments can temporarily disable parts of your code. For instance, if you think a specific line is causing an error, you can comment it out (/* code fragment */) to test the program without that line;
Comments can be used to describe how your code works, making it easier to understand later or for others working with your code.

You saw an example of commenting in the previous chapter, where a comment was placed where the code was supposed to go.

Here's another example of how to use comments:

Main


              123456789
            
package com.example;

public class Main {
    public static void main(String[] args) {
        System.out.println("Message 1");
        // System.out.println("Message 2");
	    System.out.println("Message 3");
    }
}

Only the first and third messages will be displayed here because the second part is commented out, so the compiler ignores it.

Now, let's take a look at an example of multi-line code commenting:

Main


              123456789
            
package com.example;

public class Main {
    public static void main(String[] args) {
        /* System.out.println("Message 1");
        System.out.println("Message 2"); */
        System.out.println("Message 3");
    }
}

As you can see, only the third message is displayed in the console because the first and second ones are commented out.

Uppgift

Swipe to start coding

Your task is to identify the error and comment out the code fragment that contains it.

Lösning

solution

Byt till skrivbordet för praktisk övningFortsätt där du är med ett av alternativen nedan

Var allt tydligt?

Tack för dina kommentarer!

Avsnitt 1. Kapitel 7

Byt till skrivbordet för praktisk övningFortsätt där du är med ett av alternativen nedan