Java · Beginner
Variables and Primitive Data Types
In Java, every variable must have a declared data type. 'int' is used for whole numbers, 'String' for text, and 'double' for decimal numbers.
Open snippet →Code library
Beginner Java exercises
Read these Beginner Java snippets line by line — each one comes with a written breakdown of what the code does and why.
Java · Beginner
Defining and Calling Methods
Methods are reusable blocks of code. 'void' means the method does not return a value, and parameters allow you to pass data into the method.
Open snippet →Java · Beginner
Conditional Logic with If-Else
The 'if' statement allows you to execute code only if a specific condition is true. The 'else' block provides an alternative if the condition is false.
Open snippet →Java · Beginner
Basic Class and Object Creation
In Object-Oriented Programming (OOP), a class is a blueprint. An object is an instance of that blueprint created using the 'new' keyword.
Open snippet →Java · Beginner
Iterating with For Loops
A 'for' loop is used when you know exactly how many times you want to repeat a block of code. It consists of initialization, condition, and increment.
Open snippet →Java · Beginner
The Switch Statement
The switch statement allows you to select one of many code blocks to be executed based on the value of a variable. It is often cleaner than multiple nested if-else statements.
Open snippet →Java · Beginner
String Length and Concatenation
Strings in Java are objects representing sequences of characters. You can use the length() method to find the size and the '+' operator to join strings together.
Open snippet →Java · Beginner
Basic Exception Handling
Java uses try-catch blocks to handle runtime errors (exceptions). This prevents the program from crashing by providing a way to respond to the error gracefully.
Open snippet →Java · Beginner
Iterating with While Loops
A while loop repeatedly executes a block of code as long as a given boolean condition remains true. It is useful when the number of iterations is not known in advance.
Open snippet →Java · Beginner
Declaring and Accessing Arrays
Arrays are used to store multiple values of the same type in a single variable. Elements are accessed using zero-based indexing.
Open snippet →Java · Beginner
Variables and Data Types
In Java, you must declare the type of a variable before using it. Common types include int for integers, String for text, double for decimal numbers, and boolean for true/false values.
Open snippet →Java · Beginner
Basic Conditional Logic
The 'if-else' statement allows your program to make decisions based on conditions. If the condition in the parentheses is true, the first block executes; otherwise, the else block runs.
Open snippet →Java · Beginner
The For Loop
A for loop repeats a block of code a specific number of times. It consists of initialization, a condition, and an increment step.
Open snippet →Java · Beginner
Defining a Simple Method
Methods are blocks of code that perform a specific task and can be reused. They can take parameters (input) and return a value (output).
Open snippet →Java · Beginner
Basic Class and Object
In Object-Oriented Programming (OOP), a class is a blueprint for creating objects. An object has properties (fields like name) and behaviors (methods like meow).
Open snippet →Java · Beginner
Working with Arrays
Arrays are used to store multiple values of the same data type in a single variable. You access elements using their index, starting at 0.
Open snippet →Java · Beginner
The While Loop
The while loop repeats a block of code as long as a specified boolean condition is true. It is useful when you don't know exactly how many times to loop beforehand.
Open snippet →Java · Beginner
Class Inheritance
Inheritance allows one class (child) to acquire the properties and methods of another class (parent). In Java, we use the 'extends' keyword.
Open snippet →Java · Beginner
Common String Methods
Strings in Java are objects that come with built-in methods to perform operations like checking length, changing case, or searching for text.
Open snippet →Java · Beginner
Interfaces
An interface is a contract that defines methods a class must implement. It allows for polymorphism and decoupling.
Open snippet →Java · Beginner
Method Overloading
Method overloading allows multiple methods in the same class to have the same name but different parameters.
Open snippet →Java · Beginner
Java Enums
Enums are special types that represent a fixed set of constants, making code more readable and type-safe.
Open snippet →Java · Beginner
The Final Keyword
The 'final' keyword creates constants that cannot be reassigned once initialized.
Open snippet →Java · Beginner
The Static Keyword
Static members belong to the class itself rather than individual instances, meaning they are shared by all objects.
Open snippet →Java · Beginner
The Do-While Loop
The do-while loop is a post-test loop. Unlike a regular while loop, it executes the code block first and then checks the condition, ensuring the code runs at least once.
Open snippet →Java · Beginner
The Modulus Operator (%)
The modulus operator (%) returns the remainder of a division between two numbers. It is commonly used to check if a number is even or odd.
Open snippet →Java · Beginner
The Ternary Operator
The ternary operator is a shorthand for an if-else statement. It evaluates a condition and returns one of two values based on the result.
Open snippet →Java · Beginner
Reading User Input with Scanner
The Scanner class is used to read input from various sources, such as the system console. It allows your program to interact with the user by receiving text or numbers.
Open snippet →Java · Beginner
Primitive Data Types
In Java, primitive data types are the most basic data types. They store simple values directly in memory rather than as complex objects.
Open snippet →Java · Beginner
The If-Else Statement
The if-else statement allows the program to make decisions by executing different blocks of code based on whether a condition is true or false.
Open snippet →