crossoverJie/JCSprout

JCSprout is a Java educational repository that provides concrete, runnable examples of core Java concepts and design patterns. It covers concurrency, data structures, algorithms, and JVM memory management, while also demonstrating integration with frameworks like Spring Boot, Hystrix, and Kafka. The system serves as a practical reference for understanding thread synchronization, caching, proxy patterns, and distributed system components.

24 changes.

The project was restructured into a comprehensive Java core knowledge base, establishing a Spring Boot foundation with CI integration. Significant effort was dedicated to implementing and testing diverse Java features, including concurrency, memory management, algorithms, and design patterns.

4 changes.

This period focused on expanding the library's concurrency utilities, specifically introducing a custom countdown latch for multi-threaded synchronization. The team also significantly increased test coverage by adding comprehensive unit tests for thread pools, concurrent utilities, and Java reference semantics.

Introduced new Hystrix-based command classes (CommandOrder, CommandUser) that wrap order and user service calls with thread-pool isolation and configurable execution properties. A test entry point demonstrates synchronous and asynchronous execution of these commands, showing how the library manages thread isolation and timeout handling for these specific service interactions.

src/main/java/com/crossoverjie/hystrix · high confidence

Added several new Java source files to the \com.crossoverjie.actual\ package, introducing new capabilities for thread synchronization and caching. This includes \FourThreadPrinter\ for coordinating four threads, \ThreadCommunication\ demonstrating multiple thread coordination patterns (CountDownLatch, CyclicBarrier, Piped I/O), and \TwoThread\ variants that demonstrate alternating print logic using locks, non-blocking volatile flags, and wait/notify mechanisms. Additionally, three LRU cache implementations were added: \LRUAbstractMap\ (a custom hash map with eviction and timeout), \LRULinkedMap\ (wrapping \LinkedHashMap\), and \LRUMap\ (a custom doubly-linked list based cache).

src/main/java/com/crossoverjie/actual · high confidence

Added new Java source files implementing the Chain of Responsibility pattern (including the process chain, interface, and specific handlers for copyright, sensitive words, and typos) and the Factory Method pattern (including the abstract animal class, factory interface, and concrete factories for cats and fish). These additions provide reference implementations for these design patterns within the design pattern library.

src/main/java/com/crossoverjie/design · high confidence

Added a new example implementation of the Disruptor pattern using the LMAX Disruptor library. The change introduces a complete producer-consumer workflow, including a LongEvent data class, a factory, an event handler that logs consumed events, a producer that publishes to the ring buffer, and a main class that configures the Disruptor with a single producer and a thread pool for processing.

src/main/java/com/crossoverjie/disruptor · high confidence

New Java classes, HeapOOM and MetaSpaceOOM, were added to demonstrate how to trigger and observe OutOfMemoryError conditions in the heap and metaspace (method area) respectively. The HeapOOM example continuously adds elements to an ArrayList to exhaust heap memory, while the MetaSpaceOOM example uses CGLIB to dynamically generate classes and exhaust the metaspace. These serve as practical demonstrations of JVM memory limits.

src/main/java/com/crossoverjie/oom · high confidence

A new Java class, Synchronize, was added to demonstrate basic thread synchronization using the synchronized block on the class object. This provides a concrete example of Java's built-in locking mechanism for developers.

src/main/java/com/crossoverjie/synchronize · high confidence

A new Java class, MinorGC, was added to demonstrate the behavior of the JVM's minor garbage collection when the Eden space is insufficient for memory allocation. The class configures specific JVM parameters (such as -Xms20M, -Xmx20M, -Xmn10M) to trigger a minor GC when allocating large byte arrays, providing a concrete example of memory management in the Java heap.

src/main/java/com/crossoverjie/gc · high confidence

A new RedPacket class was added to simulate the generation of red packets (in cents), ensuring each packet falls within a defined range (1 cent to 200 RMB). The implementation uses a random distribution algorithm that calculates a maximum possible value based on an average multiplied by a factor (2.1) to prevent large outliers, and recursively adjusts values to ensure the total sum is preserved while respecting min/max constraints.

src/main/java/com/crossoverjie/red · high confidence

A new Application class has been introduced to serve as the entry point for the Spring Boot application. This class is annotated with @SpringBootApplication and contains the main method that initializes the Spring application context and logs a startup confirmation message.

src/main/java/com/crossoverjie · high confidence

Added new concurrent programming utilities to the library. This includes a custom thread pool implementation (CustomThreadPool) that manages worker threads and task queues, a thread-safe array-based blocking queue (ArrayQueue), and a custom Future/Callable/FutureTask implementation to support tasks that return results. Additionally, new files demonstrate thread state management, volatile variable usage, and interrupt handling.

src/main/java/com/crossoverjie/concurrent · high confidence

Introduced a new \MultipleThreadCountDownKit\ class and a \Notify\ callback interface to enable custom countdown latches for coordinating multiple threads. The kit allows developers to set a callback that is triggered once all threads have completed their tasks, providing a flexible alternative to standard concurrency utilities.

src/main/java/com/crossoverjie/concurrent/communication · high confidence

Introduced new classes and configurations to demonstrate various ways to manage bean initialization and destruction in Spring. This includes a configuration class using XML-style init/destroy methods, a component using JSR-220 annotations (@PostConstruct/@PreDestroy), a service implementing InitializingBean/DisposableBean, a bean post-processor for pre/post-initialization hooks, and an ApplicationContextAware implementation for context access.

src/main/java/com/crossoverjie/spring · high confidence

Added new classes to demonstrate proxy patterns. For JDK dynamic proxies, added the ISubject interface, its ISubjectImpl implementation, and a CustomizeHandle invocation handler. For CGLIB-based proxies, added a RealSubject class and a RealSubjectIntercept method interceptor. These additions provide concrete examples of how to implement and intercept method calls using both JDK and CGLIB approaches.

src/main/java/com/crossoverjie/proxy · high confidence

Added three new Java classes (ChildClass, Main, SuperClass) in the com.crossoverjie.classloader package. These classes demonstrate class loading behavior, including static initialization and field access, providing a concrete example of how classloaders interact with class hierarchies.

src/main/java/com/crossoverjie/classloader · high confidence

Added several new algorithm implementations including a Bloom filter for probabilistic set membership testing, a Happy Number checker, and array right-shift logic. The update also introduces binary tree traversal and linking structures, a two-stack queue implementation, and multiple approaches for reversing and sorting linked lists.

src/main/java/com/crossoverjie/algorithm · high confidence

Added new example code for Guava's LoadingCache, including CacheLoaderTest.java which demonstrates cache expiration and removal listeners. Also added a callback mechanism example consisting of CallBackListener.java, Caller.java, Notifier.java, and Main.java, which illustrate an asynchronous notification pattern using a custom callback interface.

src/main/java/com/crossoverjie/guava · high confidence

The repository has been significantly restructured and expanded into a comprehensive Java core knowledge base (JCSprout). The README has been completely redesigned to serve as a detailed table of contents for topics including Java Collections, Multithreading, JVM, Distributed Systems, Frameworks, Architecture, Databases, Algorithms, and Netty. Additionally, a Travis CI configuration (.travis.yml) has been added to automate builds on the master branch, and a Java thread dump log (79884.log) was added to document thread states.

(repo-wide) · high confidence

The application now includes an \application.properties\ file that sets the Spring Boot application name to 'JCSprout' and configures the root logging level to INFO. Additionally, a \logback.xml\ configuration file has been added to define detailed logging behavior, including console output and rolling file appenders for DEBUG, INFO, and ERROR levels, with specific loggers configured for the 'com.crossoverjie' package.

src/main/resources · high confidence

Added Java tests for reference and value semantics; Added benchmark and utility test classes for collections, HashMap, and String; Added test for thread pool exception handling; Added tests for concurrent utilities; Added unit tests for JDK dynamic proxy implementation; Added unit tests for Kafka consumer scenarios; Added unit tests for LRU map implementations; Added unit tests for RedPacket functionality; Added unit tests for algorithm implementations.

The project is initialized with a Maven build configuration, establishing a Spring Boot 1.5.6.RELEASE parent and defining core dependencies including Spring Boot starters, CGLIB, Log4j, Apache Commons, Guava, Fastjson, Hystrix, Disruptor, Kafka, and JMH for benchmarking.

(dependencies) · high confidence

Written by watchdog.canine.dev from the codebase's own history, inside the signed delivery this page is composed from.

• CAI 61 → 60 (-1.3)
• Rubric changed (rubric-2026.08.19 → rubric-2026.09.15) — scores are not directly comparable.

• Code Health 100 → 100 (+0.2)
• Architecture 100 → 100 (+0.0)
• Maturity 45 → 45 (+0.0)
• Readiness 50 → 45 (-5.0)
• Security 100 → 100 (+0.0)

• Coverage not included — suite not readable by the collector
• Dependency hygiene not measured — dependency manifest found but not parsed for hygiene
• Duplicated block (14 lines × 2) (src/main/java/com/crossoverjie/actual/ThreadCommunication.java)
• Duplicated block (15 lines × 2) (src/main/java/com/crossoverjie/hystrix/CommandOrder.java)
• No exposed public API
• Scanner failed to run — not a clean result
• Test reliability not included
• The IdleStateHandler example uses CustomProtocol.getBean('heartBeat') but no code shows how heartBeats are received or handled by the server. (docs/netty/Netty(1)TCP-Heartbeat.md)
• dormant codebase — no living knowledge left to concentrate

• Dependency hygiene PARTLY measured — Maven/Gradle declarations read, no dependency graph resolved
• Documentation: no installation or build instructions (docs/README.md)
• Duplicated block (14 lines × 2) (src/main/java/com/crossoverjie/actual/ThreadCommunication.java)
• Duplicated block (18–19 lines × 2) (src/main/java/com/crossoverjie/hystrix/CommandOrder.java)
• No ADRs found
• No dependency advisory monitoring
• No direct assertions: clazzTest (src/test/java/com/crossoverjie/proxy/JDKProxyTest.java)
• No direct assertions: constructorOutputVoid (src/test/java/com/crossoverjie/algorithm/LinkedListMergeSortTest.java)
• No direct assertions: consumer (src/test/java/com/crossoverjie/kafka/KafkaTest.java)
• No direct assertions: execute (src/test/java/com/crossoverjie/concurrent/CustomThreadPoolExeceptionTest.java)
• No direct assertions: execute (src/test/java/com/crossoverjie/concurrent/CustomThreadPoolFutureTest.java)
• No direct assertions: execute (src/test/java/com/crossoverjie/concurrent/CustomThreadPoolTest.java)
• No direct assertions: get (src/test/java/com/crossoverjie/actual/LRULinkedMapTest.java)
• No direct assertions: get (src/test/java/com/crossoverjie/actual/LRUMapTest.java)
• No direct assertions: get2 (src/test/java/com/crossoverjie/actual/LRUMapTest.java)
• No direct assertions: get2 (src/test/java/com/crossoverjie/concurrent/ArrayQueueTest.java)
• No direct assertions: get3 (src/test/java/com/crossoverjie/actual/LRUMapTest.java)
• No direct assertions: get4 (src/test/java/com/crossoverjie/actual/LRUMapTest.java)
• No direct assertions: getTwo1 (src/test/java/com/crossoverjie/algorithm/TwoSumTest.java)
• No direct assertions: getTwo2 (src/test/java/com/crossoverjie/algorithm/TwoSumTest.java)
• …and 37 more

Written by watchdog.canine.dev from the codebase's own history, inside the signed delivery this page is composed from.

crossoverJie/JCSprout was measured the same way every project in this corpus was: the same rubric, at a pinned commit, with the result published in full. Point a surveyor at a repository you know and see whether you agree with it.