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Interpreter: sync post code blocks to repo exactly (Javadoc wording), H6 file labels + explanatory paragraphs between every block, Java 25 note, README mapping

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03-behavioral/interpreter/README.md Normal file
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# Interpreter Design Pattern — Java Example
**Pattern:** Behavioral → Interpreter
**Article:** https://ankurm.com/interpreter-design-pattern-java/
## What this example shows
A math expression evaluator built as an abstract syntax tree. `Expression` declares `interpret()` — every AST node implements it. `NumberExpression` is the only terminal: a leaf with no children that returns its value directly. `AddExpression`, `SubtractExpression`, and `MultiplyExpression` are non-terminals: each holds two child expressions and applies its operator after recursively interpreting them. `Main` is the client — it assembles three small trees by hand (`(5 + 3) * 2`, `10 - (4 + 2)`, `(3 * 4) + (10 - 6)`) and evaluates each by calling `interpret()` on the root.
## How to run
```bash
javac interpreter/*.java -d out/interpreter
java -cp out/interpreter interpreter.Main
```
Requires Java 25.
## Post Section ↔ File Mapping
| Post Section | File(s) |
|---|---|
| Implementation: Math Expression Evaluator — the AbstractExpression | `Expression.java` |
| Implementation: Math Expression Evaluator — the TerminalExpression | `NumberExpression.java` |
| Implementation: Math Expression Evaluator — AddExpression | `AddExpression.java` |
| Implementation: Math Expression Evaluator — SubtractExpression | `SubtractExpression.java` |
| Implementation: Math Expression Evaluator — MultiplyExpression | `MultiplyExpression.java` |
| Implementation: Math Expression Evaluator — wiring it together | `Main.java` |
Article: https://ankurm.com/interpreter-design-pattern-java/
All patterns: https://ankurm.com/design-patterns-java/

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README.md
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java -cp out/visitor visitor.Main
```
### Interpreter (`03-behavioral/interpreter/`)
| Post Section | File(s) |
|---|---|
| Implementation: Math Expression Evaluator — the AbstractExpression | `Expression.java` |
| Implementation: Math Expression Evaluator — the TerminalExpression | `NumberExpression.java` |
| Implementation: Math Expression Evaluator — AddExpression | `AddExpression.java` |
| Implementation: Math Expression Evaluator — SubtractExpression | `SubtractExpression.java` |
| Implementation: Math Expression Evaluator — MultiplyExpression | `MultiplyExpression.java` |
| Implementation: Math Expression Evaluator — wiring it together | `Main.java` |
Run it:
```bash
javac 03-behavioral/interpreter/*.java -d out/interpreter
java -cp out/interpreter interpreter.Main
```
## Reference
- *Design Patterns: Elements of Reusable Object-Oriented Software* — Gamma, Helm, Johnson, Vlissides