# Command Design Pattern — Java Example

**Pattern:** Behavioral → Command
**Article:** https://ankurm.com/command-design-pattern-java/

## What this example shows

A text editor with full undo support. `Command` declares `execute()`/`undo()`/`getDescription()`. `InsertCommand` and `DeleteCommand` are concrete commands that call back into the receiver, `TextEditor`. `DeleteCommand` captures the text it's about to delete *before* deleting it, so `undo()` can restore it. `CommandHistory` is the invoker: it pushes executed commands onto a stack and pops/undoes them on request, without knowing what any command actually does.

## How to run

```bash
javac command/*.java -d out/command
java -cp out/command command.Main
```

Requires Java 25.

## Post Section ↔ File Mapping

| Post Section | File(s) |
|---|---|
| Step 1 — Command Interface | `Command.java` |
| Step 2 — The Receiver (TextEditor) | `TextEditor.java` |
| Step 3 — Concrete Commands | `InsertCommand.java`, `DeleteCommand.java` |
| Step 4 — The Invoker (CommandHistory) | `CommandHistory.java` |
| Demo | `Main.java` |

Note: the `MacroCommand` snippet (Composite applied to Command) and the `Runnable`/`Callable`/`CompletableFuture` JDK snippets are illustrative only — they are not part of this repository's runnable example.

Article: https://ankurm.com/command-design-pattern-java/
All patterns: https://ankurm.com/design-patterns-java/