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Learn Structured tracks from core Java through Spring Boot, JPA and Kafka. Your progress follows you. Open the roadmap Topics Short, focused write-ups for when one concept is the only thing in your way. Browse topics Java Sandbox Write, compile and run Java in the browser. No JDK, no project, output in about a second. Run some Java Spring Boot Sandbox Start a real Spring Boot app and call its REST endpoints - from this page or from Postman. Start a sandbox Spring Boot + Database The same sandbox with a PostgreSQL database that is still there tomorrow. Browse the tables, run SQL. Open the DB sandbox Kafka Lab Produce to a real topic and watch a live consumer receive it. Your broker or ours, partitions, headers and offsets included. Send a message Projects Production-shaped projects, documented and downloadable, ready to build and run. Explore projects Interview Question banks for Java, Spring Boot, Microservices and Kafka, plus an AI interviewer that asks follow-ups. Practise interviews Free Tools JSON, JWT, regex, cron, OpenAPI to Java and more. All free, and none of them ask you to sign in. Open the tools
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Popular: Difference Checker · JSON Formatter · JWT Decoder · JSON to Java POJO · JSON to Java Record · YAML to JSON · Properties to YAML · Base64 Encoder · OpenAPI to Java DTO · OpenAPI to Spring Controller · OpenAPI to Postman · UUID Generator · Cron Generator · Timestamp Converter · HTTP Request Builder · Kafka Partition Calculator · Kafka Message Size · SQL Formatter

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