Arrays
Creating and using fixed length arrays. Find out how combining them with for loops can make your programs easier to understand! The example is creating an array of lottery numbers.
Array Lists
How to use Java's ArrayLists. These are dynamic arrays that you can add and remove items to. Like arrays, they can help simplify your code. The example is creating and adding to a list of planets.
Files - Reading a Binary File
All New! 28/06/2026
How to safely read from a binary file. The example shows how to check that a bitmap file really
is a bitmap file by reading the file header.
Files - Reading a Text File
All New! 28/06/2026
How to safely read through a text file line by line after first checking it exists and then handling any problems.
Methods
Methods (sometimes called functions) are self contained blocks of code that can help with code organisation and can be called multiple times reducing duplication. The example shows a method to calculate the area of a rectangle.
Strings
Strings are one of the most commonly used data types, learn how to create and use them effectively! The example demonstrates creating and modifying strings.
Strings - Comparing
This guide shows how to compare Strings the correct way using the equals method.
Strings - Splitting
Splitting Strings is very useful, this page shows how to split a string of numbers and add them together. It also shows how to convert a String to a number and how an exception is raised if it fails.
StringBuilder
Find out how to use StringBuilder to join Strings faster and more efficiently. The example shows timings between joining Strings using the '+' and with StringBuilder. The StringBuilder method can be up to 100x faster!
Console Input
Getting typed input from the user, also find out how to convert Strings to numbers. The example gets the age of the user and works out the year they were (probably) born in.