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Python 3.15 adds the lazy keyword (PEP 810) for imports that load on first use. This guide measures start-up time with -X importtime, shows a CLI tool that starts in 57 ms instead of 141 ms, and compares the older alternatives.
Context bloat is the growth of an LLM request with tokens the model does not need. Measure a real agent request and cut it with six techniques.
Python 3.15 makes UTF-8 the default encoding of open() on every platform. What breaks with cp1252 files on Windows, and the six steps to migrate safely.
Stateless MCP means every request carries what the server needs. What revision 2026-07-28 removed and added, shown with a stateful and a stateless Python server behind a two-instance proxy.
Upgrade the Python version of an existing project in seven steps with pip and venv: fix the deprecation warnings on the old version, check the wheels, test on both versions, then switch. Shown on a real project moving from 3.12 to 3.15.
A SKILL.md file holds on-demand instructions for a coding agent. This guide covers the format, the description that triggers it, a validator and two tests.
Fix the Dropwizard error Failed to parse configuration, could not resolve type id ‘http’ as a subtype of ConnectorFactory: add the Shade services merge.
Dropwizard health check examples with a custom HealthCheck, the admin /healthcheck, the health block in config.yml, Kubernetes probes and JUnit tests.
Dropwizard tutorial with a hello world REST API on Dropwizard 5 and Java 25: configuration, resources, fat JAR, ports, health check and JUnit 6 tests.
Dropwizard basic auth example with dropwizard-auth: Authenticator, Authorizer, BCrypt password hashes, @RolesAllowed, caching and tests for 401 and 403.
Dropwizard client guide with JerseyClientBuilder, HttpClientBuilder and config.yml settings for timeouts, connection pool, retries, gzip, TLS and tests.
Compare ten machine learning libraries for Java by version, license, minimum Java and maintenance status, with Smile and Tribuo examples and a pick-by-situation table.
Estimate LLM token costs in Java with current OpenAI, Anthropic and Gemini prices, read real token usage with Spring AI, and cut the bill with prompt caching.
Learn what the Model Context Protocol (MCP) is, how hosts, clients and servers exchange JSON-RPC messages, and how to build an MCP server and client in Java.
LLM terms for Java developers, from tokens and context windows to temperature, embeddings, RAG, tool calling and MCP, with Spring AI classes.
JUnit 5 vs JUnit 6 compared, with the Java 17 baseline, removed APIs, migration steps for Maven and Gradle, OpenRewrite and runtime changes.
What is data analytics? Learn the four types, the six-step process, the skills and free tools to start with, and a first analysis in SQL and Python.
Compare IntelliJ IDEA, VS Code, Eclipse, Cursor and Devin Desktop for AI-assisted Java development in 2026. AI models, free tiers, pricing, testing and CI/CD support at a glance.
@GetMapping maps HTTP GET requests and @PostMapping maps HTTP POST requests to controller methods in Spring. Both are shortcuts for @RequestMapping with a fixed HTTP method.
Two strings are isomorphic when a one-to-one character mapping turns one into the other. Learn the algorithm and check it in Java with arrays or two HashMaps.
Spring Authorization Server issues OAuth2 access tokens and OpenID Connect ID tokens from our own Spring Boot application. This tutorial builds an authorization server and a resource server on Spring Boot 4.1, with client_credentials and PKCE clients, key rotation, custom claims, JDBC client storage, MockMvc tests and real curl output.
Thymeleaf renders server-side HTML pages from natural templates in a Spring Boot application. This tutorial builds a playlist app on Spring Boot 4.1.1 and Thymeleaf 3.1.5 with loops, conditions, links, validated forms, fragments, i18n and date and number formatting, and tests the views with MockMvcTester.
Embabel tutorial for Spring Boot 4: build a GOAP-planned agent with @Action, conditions and tools, run it on Ollama and test it without an API key.
ArchUnit checks the structure of Java code, such as layers, package cycles, naming and Spring annotations, inside ordinary JUnit 6 tests. This tutorial sets up archunit-junit6 1.5.1, writes layered, onion and Spring Boot rules, reads real failure messages and freezes rules for legacy code.
AssertJ is a Java assertion library where we chain readable checks on assertThat(actual) and get failure messages that name the exact difference. This tutorial covers strings, numbers, collections, maps, Optional, exceptions, records, java.time, soft assertions, custom assertions and MockMvcTester in Spring Boot, with a cheat sheet table.
Spring Cloud Gateway puts one entry point in front of our microservices and routes each request with predicates and filters. This tutorial builds a complete gateway on Spring Boot 4.1 with YAML and Java routes, Redis rate limiting, retry, a Resilience4j circuit breaker, CORS, WireMock tests and the actuator endpoints.
A module import declaration such as import module java.base; imports every package a module exports with one line, and it is final in Java 25. Learn what it imports, how to fix “reference to List is ambiguous” with a single-type import, and how it works with java.se and compact source files.
TypeScript utility types create new types from an existing one, such as an all-optional copy or a subset of keys. This reference lists all 22 built-in utility types with their results, gives one example each for Partial, Pick, Omit, Record, Exclude, ReturnType and Awaited, and shows the real tsc errors we get when we use them wrong.
java.lang.NoSuchMethodError means code compiled against one version of a class runs with another version that lacks the called method. Learn to read the message, find the wrong jar with mvn dependency:tree, -verbose:class and javap, and fix the conflict with a BOM, an exclusion and the Enforcer dependencyConvergence rule.
A StackOverflowError means a thread made more nested calls than its stack can hold. Learn to read the repeating stack trace, fix missing base cases, deep recursion and object cycles in toString(), Lombok and Jackson, and when -Xss helps.
IllegalArgumentException is the unchecked exception a Java method throws when an argument has a value it does not accept. This post lists the JDK calls that throw it with their real Java 25 messages and the fix for each, the subclasses such as NumberFormatException, and when our own code should throw it instead of IllegalStateException or NullPointerException.
The TypeScript satisfies operator checks a value against a type and keeps the narrow type TypeScript inferred for it. We compare satisfies with type annotations and as assertions, use it on settings objects, Record maps and as const tables, and read the real tsc errors for the common mistakes.
Spring Boot microservices are small Spring Boot applications that each own one business capability and call each other over the network. This tutorial builds a complete library system on Spring Boot 4.1 with Spring Cloud Gateway, HTTP interface clients, Resilience4j retry and circuit breaker, OpenTelemetry tracing with one trace id across services, Docker Compose and WireMock tests, and explains when not to use microservices.
A CompletableFuture is a Future that runs the next step when its result arrives, so no thread has to wait for it. This tutorial creates, chains and combines CompletableFuture tasks on virtual threads, handles errors and timeouts, and shows the mistakes that make async code hang or lose exceptions.
A TypeScript decorator is a function that we put above a class or class member with @name, and it can replace that member with a new version. Learn each decorator kind with runnable TypeScript 7 examples, the order decorators run in, the usual compiler errors, and how standard decorators differ from experimentalDecorators used by Angular, NestJS and TypeORM.
Kafka queues let many consumers in a share group read the same partition and acknowledge each record on its own. This guide compares share groups with consumer groups, lists the status in Kafka 4.x and the broker settings, and builds a Spring Kafka share consumer with acknowledge, release and reject.
Spring Boot 4 is the major release built on Spring Framework 7, Jakarta EE 11 and Jackson 3, with Java 17 as the minimum. This tutorial builds one Spring Boot 4.1.1 app that shows the modular starters, JSpecify null-safety with NullAway, API versioning, HTTP service clients with @Retryable, Jackson 3, MockMvcTester and RestTestClient tests, virtual threads, OpenTelemetry traces and the 4.1 additions, and ends with an upgrade checklist from Spring Boot 3.5.
TypeScript 6 is the last TypeScript release with a JavaScript-based compiler. It changes tsconfig.json defaults such as strict and types, and deprecates options that TypeScript 7 removes. This overview lists every change with the real tsc errors and an upgrade checklist for 5.x projects.
TypeScript 7 is the Go port of the TypeScript compiler and checks the same language as TypeScript 6 about 10 times faster. We compare both versions in a table, time tsc 6.0.3 and tsc 7.0.2 on the same project, and show what still needs TypeScript 6 and how to switch.
Spring Framework 7 keeps Java 17 but moves to Jakarta EE 11, JSpecify null-safety and Jackson 3. This overview lists every notable change in a summary table and shows the main new features, such as @Retryable, API versioning and BeanRegistrar, with short examples.
Jackson 3 moves to the tools.jackson group id and packages, makes JsonMapper immutable and replaces the checked JsonProcessingException with JacksonException. This guide shows each change with a short snippet, the changed defaults side by side, how Spring Boot 4 uses Jackson 3, and a migration checklist.
Gradle 9 needs Java 17 or newer to run, builds scripts with Kotlin 2 and Groovy 4, and removes the APIs that Gradle 8 deprecated. This overview lists the main changes from 9.0 to 9.8.0, builds a Java 25 project with the Gradle 9 wrapper, and fixes the most common upgrade errors.
Mockito 5 creates mocks for a class’s dependencies and mocks final classes and static methods with mockito-core alone. This tutorial sets up Mockito 5.24.0 with JUnit 6 on Java 25, including the Java agent setup, and covers stubbing, verify, matchers, captors, spies, mockStatic and the strict stubs errors.
Spring Security 7 ships with Spring Boot 4 and removes the APIs deprecated in 6.x, such as and() chaining and AntPathRequestMatcher. This overview lists every change in one table, explains each one briefly with snippets for the main ones, and ends with a migration checklist from 6.x.
A Java 25 migration is mostly a build change. This step-by-step guide upgrades a Maven project from Java 21 to Java 25, shows the support dates, and fixes the real errors from Lombok, Mockito and JaCoCo on the way.
Java 25 is the LTS release of September 2025 with 18 JEPs. This guide runs every one of them, from compact source files, module imports, flexible constructors and scoped values to compact object headers, AOT caches and the new JFR events, and shows the preview features with their –enable-preview flags. It ends with the features that became final between Java 21 and 25 and a migration checklist.
Java 26 (JDK 26) shipped on 17 March 2026 as a non-LTS release with 10 JEPs. This overview lists every JEP with its status and shows short, runnable examples for HTTP/3, final field warnings, the AOT cache with ZGC and the preview APIs.
Java 27 (JDK 27) reached general availability on 15 September 2026 with nine JEPs. Four final JEPs change JVM defaults (G1 everywhere, compact object headers, post-quantum TLS, JFR redaction), and five continue as previews or incubator. A summary table, one example per feature and the removed options.
Initialize a Java List in one line with List.of() for an unmodifiable list, or new ArrayList<>(List.of(…)) when the list changes later. Compare Arrays.asList(), Stream.toList(), Collections and Guava by mutability and null support.
Maven 4 separates the build POM from the published consumer POM, which brings POM model 4.1.0, subprojects, inferred versions, BOM packaging and new lifecycle phases. Maven 4.0.0 is still a release candidate (4.0.0-rc-7), so this guide builds the same project with Maven 3.9.16, 3.10.0 and 4.0.0-rc-7, shows what fails and walks through the migration with mvnup.
HowToDoInJava provides tutorials and how-to guides on Java and related technologies.
It also shares the best practices, algorithms & solutions and frequently asked interview questions.
