Course description

If you want a first programming language that employers use for real business systems, this course teaches Java from the very beginning, one clear step at a time, until you can plan and build a complete program with objects.

You start by installing a free JDK and running a program from the command line, then learn the building blocks: variables and types, text, decisions, loops and methods. From Section 6 you work with objects: classes, constructors, private fields, inheritance, interfaces, records and enums. Then you handle problems with exceptions, store data in lists, maps and sets, read and write files, organise code into packages, read error messages with confidence and pick up the habits that keep code clear and checked.

There are 10 sections and 50 written lessons, each with real code and its real output, a worked example, common slips, questions people often ask and a short exercise to try, and each section ends with a short quiz. You follow Roshni, a warehouse shift supervisor learning Java, as she builds a loans manager for the volunteers at a fictional tool library. Every section has a practice pack with starter files, worked answers, expected output, a worksheet with an answer key and a cheat sheet. Pack 1 and pack 10 add a Java syntax card, pack 9 adds a guide to error messages, and pack 10 holds the final project in six step folders.

What you'll learn

• Getting started with Java: what Java is, the JDK and the JVM, installing a JDK from an official source, and compiling and running your first program from the command line.
• Variables, types and operators: the main types, arithmetic with whole numbers and decimals, converting between types, comparisons and logic, constants, and money kept in pence.
• Strings, input and output: String methods, comparing and building text, neat output with printf, and reading and checking what someone types.
• Decisions and loops: if and else, switch in its classic and newer forms, while, do-while and for loops, and a simple menu.
• Methods, arrays and ArrayList: writing your own methods, parameters and return values, arrays, lists that grow, and splitting a program into small steps.
• Classes and objects: classes as blueprints, constructors, instance methods, private fields with getters and setters, toString and equals.
• Inheritance, interfaces, records and enums: subclasses and overriding, interfaces, polymorphism, and the shorter forms records and enums.
• Exceptions, collections and generics: catching and throwing exceptions, lists, maps and sets, what the angle brackets mean, and sorting.
• Files, packages, debugging and good habits: reading and writing text files, dates, packages, reading error messages, debugging, and the habits that keep code readable and checked.
• Final project: the tool library loans manager: a complete console program for a made-up tool library, planned and built in six working steps, with the full code at every step.

Who it's for

Career changers, students and adults who want a first programming language for work. You don't need any programming experience: just a computer where you can install free software, and the patience to type code carefully. If you'd rather start with a language that has less to set up, Python for Beginners: Write Real Programs from Scratch is another good first step.

What this course is, and isn't

This is a practical introduction to Java and object-oriented programming, using the command line and plain text files, so you understand every step. It teaches Java 21, a long-term support release, and every code sample was compiled and run with OpenJDK 21; newer versions exist and run the same code. It isn't a course on building web sites, mobile apps or graphical windows, and it doesn't depend on any particular editor. Roshni and every other person and organisation in the course are fictional.

What will I learn?

• Install a JDK, then compile and run Java programs from the command line with javac and java
• Use variables, the main types, arithmetic, comparisons and constants, and keep money exact in whole pence
• Work with Strings, format output neatly with printf and read and check what someone types
• Make decisions with if and switch, and repeat work with while, do-while and for loops
• Split programs into methods, and store values in arrays and ArrayLists
• Design classes with private fields, constructors and methods, and make objects from them
• Use inheritance, interfaces and polymorphism, and the shorter forms records and enums
• Handle problems with exceptions, and store data in lists, maps and sets with simple generics
• Read and write text files, organise code into packages, read error messages and debug with confidence
• Plan and build a complete console program for a small organisation, step by step, with full code

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