Java

Java powers enterprise apps, Android builds, and backend systems through its "write once, run anywhere" runtime and strong tooling.

Reserved Words

• abstract, assert, boolean, break, byte
• case, catch, char, class, const, continue
• default, do, double
• else, enum, extends
• final, finally, float, for
• goto, if, implements, import, instanceof, int, interface
• long, native, new
• package, private, protected, public
• return, short, static, strictfp, super, switch, synchronized
• this, throw, throws, transient, try
• void, volatile, while
• true, false, null (literals)

Platform Pillars

• JVM bytecode executes on HotSpot, OpenJ9, GraalVM, and Azul runtimes.
• Garbage collection options include G1, ZGC, Shenandoah, Serial, Parallel.
• Modular JDK (JPMS) decomposes the platform for smaller deployments.
• JIT and AOT modes deliver adaptive performance.

Language Features

• Generics with type erasure and bounded wildcards (`List`).
• Records, sealed classes, and pattern matching (JEP 440+) streamline modeling.
• Lambda expressions fuel Streams API for declarative data pipelines.
• Virtual threads (Project Loom) scale structured concurrency.
• Switch expressions and text blocks reduce boilerplate.

Core APIs

• java.lang: Object, String, Math, records, enums.
• java.util: collections, Optional, concurrent data structures.
• java.time: immutable ISO-8601 clocks.
• java.net.http: HTTP/2 client with WebSocket support.
• java.nio: buffers, channels, file walking.
• Spring, Micronaut, Quarkus, Jakarta EE extend cloud features.

Operators

• Arithmetic: + - * / % ++ --
• Comparison: == != > < >= <=
• Logical: && || !
• Bitwise: & | ^ ~ << >> >>>
• Assignment: = += -= *= /= %= &= |= ^= <<= >>= >>>=
• Instance checks: instanceof, pattern matching `instanceof Point(var x, var y)`.

Build & Tooling

• Gradle, Maven, and Bazel orchestrate builds, dependency graphs, and publishing.
• JLink creates trimmed runtime images; JPackage ships native installers.
• Testing ecosystems: JUnit 5, TestNG, AssertJ, Mockito, WireMock.
• Observability: Flight Recorder, Mission Control, async-profiler.

Best Practices

• Favor immutable data and builder patterns to reduce defensive copies.
• Use `var` for local inference where it clarifies types.
• Run SpotBugs, Error Prone, and Checkstyle in CI for safety.
• Package microservices with layered Docker images and JDK 21 LTS.

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