A reference of everyday Java, from strings and collections to threading and design patterns. Every example comes with an explanation, and most of them run. • 22 sections: simple types, arrays and collections, classes, interfaces and generics, functions and lambdas, files, serialization, exceptions, regular expressions, threading, databases, patterns. • Run in the app: the example really executes and the output appears under the code. Needs an internet connection. • What changed in new versions: 8 sections from Java 9 to 21, with "before" and "after" code side by side. • Keyword and function reference: 160 articles, fully open with no daily counter. • SQL alongside: over 200 queries against a live practice database - JOIN, GROUP BY, subqueries, data types. • Edit examples and add your own - they stay in the app and are always at hand. • Search runs over the code itself, not just the titles: remember a fragment and you will find the example. • Everything except running works offline. No account needed. WHAT THE FREE VERSION INCLUDES 12 runs and 12 edits a day - the counter resets every morning. The keyword reference is open without limits. Up to 5 examples of your own. Copying in the free app is blocked after five attempts. The full version opens every example, removes the daily limits and raises running to 30 launches a day. One purchase, no subscription. Made by a developer for developers. In development since 2015.