01 · Java
Install Java and run the first program
Compile a Java file and run the resulting program.
54 Tutorials · DE / EN
Learn to code: Java
Start with no prior knowledge. Small examples explain the language. Medium guides connect building blocks. Large tutorials walk through complete project workflows.
Java
Small
02 · Java
Variables and data types in Java
Distinguish primitive values, text and missing references.
03 · Java
Operators and conditions
Check numbers and text using appropriate comparisons.
04 · Java
Loops and controlled repetition
Process a sequence of values using one shared rule.
05 · Java
Methods, parameters and results
Separate a calculation from its output.
06 · Java
Arrays, lists, sets and maps
Choose a collection for ordering, uniqueness or lookup.
07 · Java
Classes and constructors
Create a custom data type with controlled initial values.
08 · Java
Interfaces and composition
Define a contract and replace its implementation.
09 · Java
Exceptions and safe file access
Handle a failure and close a file even when work stops.
Medium
10 · Java
Maven, modules and ports/adapters
Understand a Java build and dependency direction.
11 · Java
Read CSV and fill PDF forms
Read structured CSV fields and set an AcroForm value using PDFBox.
12 · Java
JDBC, SQLite and local transactions
Store a record through JDBC and understand a migration’s responsibility.
13 · Java
Spring Boot REST with validation
Receive JSON, validate input and return an appropriate HTTP status.
14 · Java
Understand PostgreSQL, JPA and Flyway
Distinguish database schema, object mapping and transaction boundaries.
15 · Java
JUnit, semantic PDF tests and Testcontainers
Verify the contents of a real PDF and choose tests according to the guarantee being demonstrated.
Large
16 · Java
Offline PDF workflow with JavaFX and SQLite
Follow template, mapping, preview, background jobs and local project persistence through a real desktop app.
17 · Java
Spring Boot batch workflow with uploads and Docker
Follow a stored upload through configuration, processing, download and cleanup.
18 · Java
Idempotency, outbox and reliable retries
Recognise duplicate requests and connect a database commit to later event delivery.