Practitioner

15 labs covering intermediate Java 21: generics, streams, functional interfaces, concurrency, file I/O, JDBC, design patterns, reflection, enums, and a full capstone order platform.

Labs

#	Lab	Key Skills
01	Generics & Collections	Bounded types, PECS wildcards, TreeMap, PriorityQueue, computeIfAbsent
02	Streams & Lambdas	filter/map/flatMap/reduce, Collectors.groupingBy, partitioningBy, toMap
03	Functional Interfaces	Function, Predicate, Optional, composition, method references
04	Exception Handling	Custom hierarchy, multi-catch, Result<T> sealed type, finally
05	Concurrency	ExecutorService, CompletableFuture, ConcurrentHashMap, CAS
06	File I/O & NIO.2	Path, Files.lines, Files.walk, BufferedWriter, file attributes
07	Java 21 Features	Records, sealed interfaces, pattern matching switch, text blocks
08	Design Patterns	Builder, Factory, Observer (EventBus), Strategy
09	Testing	assertEquals, assertApprox, assertThrows, parametrized tests
10	JDBC & SQLite	PreparedStatement, batch insert, transactions, JOIN queries
11	HTTP Client	java.net.http, GET/POST, async parallel, retry/backoff
12	Reflection & Annotations	@Retention, @Target, SQL generator, generic repository
13	Interfaces Advanced	Default/static/private methods, composition, template method
14	Advanced Enums	State machine, abstract methods, EnumSet, EnumMap, exhaustive switch
15	Capstone — Order Platform	All patterns: records + sealed + enums + concurrency + streams + events

Prerequisites

• Java Foundations Labs 01–15 (all)

• Java 21 (Eclipse Temurin) — zchencow/innozverse-java:latest

Run Any Lab

docker pull zchencow/innozverse-java:latest

# Inline code
docker run --rm zchencow/innozverse-java:latest sh -c "
cat > /tmp/Main.java << 'EOF'
public class Main {
  public static void main(String[] args) {
    System.out.println(\"Java \" + Runtime.version());
  }
}
EOF
javac /tmp/Main.java -d /tmp && java -cp /tmp Main"

# From file
docker run --rm -v /tmp/MyLab.java:/tmp/MyLab.java zchencow/innozverse-java:latest \
  sh -c "javac /tmp/MyLab.java -d /tmp && java -cp /tmp MyLab"