Apa bedane antara JVM, JRE lan JDK?

Question

Accepted Answer

Telung akronim kasebut nggambarake lapisan-lapisan bersarang saka platform Java. Cara paling gampang kanggo ngingat: **JDK ngemot JRE, kang ngemot JVM** — saben-benene nambah kemampuan marang apa sing ana ing dalam.

## Ngapa penting

Pahami bedane JVM/JRE/JDK menerangake arsitektur platform Java lan menjawab pitakon praktek: pengembang nginstal **JDK** (kanggo ngompilasi lan nglakoni), **JVM** apa sing tenan-tenan ngeksekusi bytecode lan ngaktifake kemerdekaan platform + waste collection, lan **JRE** sacara sejarah mung nyediakake runtime kanggo ngeksekusi app.

Model berlapis iki nerangake apa Kode Java dadi saka sumber menyang program sing mlaku, mengapa WORA makarya (lapisan JVM), lan apa sing kudu dipasang kanggo tugas tartamtu — pengetahuan dhasar kanggo nyiapake lan dipikir babagan lingkungan Java apa wae.

## Saranganing

```text
┌─────────────────────────── JDK (Development Kit) ───────────────────┐
│  javac (compiler), debugger, javadoc, jar, other dev tools          │
│  ┌─────────────────────── JRE (Runtime Environment) ─────────────┐  │
│  │  Java class libraries (standard API: java.util, java.io, ...)  │  │
│  │  ┌──────────────────── JVM (Virtual Machine) ───────────────┐  │  │
│  │  │  Executes bytecode, JIT compilation, garbage collection   │  │  │
│  │  └───────────────────────────────────────────────────────────┘  │  │
│  └─────────────────────────────────────────────────────────────────┘  │
└────────────────────────────────────────────────────────────────────────┘
```

## JVM — Java Virtual Machine (mesin runtime)

```text
Executes the bytecode. Responsibilities:
  ✓ Loads .class files, verifies bytecode
  ✓ Interprets / JIT-compiles bytecode to native machine code
  ✓ Manages memory & garbage collection
It's the layer that makes "write once, run anywhere" work — platform-specific
JVMs run the SAME bytecode.
```

## JRE — Java Runtime Environment (KANGGO NGJALANAKE app)

```text
JVM + the standard class libraries (the built-in API your code calls).
What you need to RUN a Java application — but NOT to compile one.
```

## JDK — Java Development Kit (KANGGO NGBANGUN app)

```text
JRE + development tools:
  javac   — the compiler (.java → .class bytecode)
  jdb     — debugger
  javadoc — documentation generator
  jar     — packaging tool
What a DEVELOPER needs to write, compile, and build Java programs.
```

## Apa sing butuh?

```text
Writing/compiling Java code  → JDK (it includes everything)
Only running a Java app      → JRE was historically enough
  (modern Java often bundles the runtime; JRE is less separately distributed now)
```