Learn Java
five minutes at a time.

public class Main {
    public static void main(String[] args) {
        System.out.println("Hello, Pebble!");
    }
}

Hello, Pebble!

The Codiqo Java course starts at System.out.println() and covers variables, conditions, loops, arrays, methods, collections, classes, inheritance and interfaces. Every example was compiled with every warning switched on.

How the Java lessons work

The full Java curriculum

1. Foundations

   Output, variables, types, input and logic.

   First Steps: Write your first Java programs.

   • Hello, Java: Write a class with main() and print with System.out.println
   • Variables and Types: Store values in int, double, boolean, char and String
   • Arithmetic: Calculate with + - * / % and predict integer division
   • Formatting Output: Use print, printf and comments

   Text and Input: Work with Strings and read input.

   • Strings and Concatenation: Join text and values
   • String Methods: Use length, charAt, substring, indexOf and more
   • Reading Input with Scanner: Read numbers and lines from the keyboard
   • Project: Tip Calculator: Calculate and format a bill split

   Logic: Make true or false decisions.

   • Comparisons and boolean: Compare values and store booleans
   • Logical Operators: Combine conditions with && || and !
   • Casting and Math: Convert types and use the Math class
   • Project: Eligibility Checker: Decide eligibility from several conditions

2. Control Flow

   Decisions, loops and methods.

   Making Decisions: Run different code depending on conditions.

   • if and else: Run code only when a condition is true
   • else if and Nesting: Choose between several paths
   • switch: Use classic and arrow-style switch
   • Project: Grade Calculator: Turn scores into grades

   Loops: Repeat work with while and for.

   • while and do-while: Repeat while a condition is true
   • for Loops: Count with for and nest loops
   • break and continue: Leave loops early and skip iterations
   • Project: FizzBuzz: Solve the classic FizzBuzz problem

   Methods: Reuse code with methods.

   • Defining Methods: Write and call static methods
   • Parameters and Return Values: Pass values in and get results out
   • Overloading and Scope: Overload methods and understand local variables
   • Project: Temperature Converter: Build a converter from small methods

3. Data and Collections

   Arrays, lists, maps and strings.

   Arrays: Store many values of the same type.

   • Creating Arrays: Create arrays and read and change items
   • Looping over Arrays: Total, search and use the Arrays class
   • 2D Arrays: Work with grids of values
   • Project: Score Statistics: Summarise a list of scores

   Collections: Use ArrayList and HashMap.

   • ArrayList: Grow and shrink lists of objects
   • HashMap: Look up values by key
   • Iterating Collections: Loop over lists and map entries
   • Project: Word Counter: Count the words in a piece of text

   Working with Text: Compare, build and split strings.

   • equals versus ==: Compare strings correctly
   • StringBuilder: Build text efficiently
   • Splitting and Joining: Break text apart and put it back together
   • Project: Text Analyzer: Report statistics about a sentence

4. Object-Oriented Java

   Classes, inheritance, interfaces, errors and a complete project.

   Classes and Objects: Model things with your own classes.

   • Classes, Fields and Constructors: Define a class and create objects
   • Methods and this: Give objects behaviour
   • Encapsulation: Use private fields with getters and setters
   • Project: Bank Account: Model an account with safe deposits and withdrawals

   Inheritance and Interfaces: Share behaviour and handle problems.

   • Inheritance: Extend classes and override methods
   • Interfaces and Polymorphism: Program to an interface
   • Exceptions: Throw, catch and create exceptions
   • Project: Shapes: Compute areas through a shared interface

   Capstone Project: Plan and build a complete Java program.

   • Planning and Modelling: Turn an idea into classes
   • Core Logic: Implement the main features
   • Errors and Testing: Handle bad input and check behaviour
   • Polishing: Improve output, structure and readability

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