33 lines
1.4 KiB
Markdown
33 lines
1.4 KiB
Markdown
# Command Design Pattern — Java Example
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**Pattern:** Behavioral → Command
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**Article:** https://ankurm.com/command-design-pattern-java/
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## What this example shows
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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.
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## How to run
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```bash
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javac command/*.java -d out/command
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java -cp out/command command.Main
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```
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Requires Java 25.
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## Post Section ↔ File Mapping
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| Post Section | File(s) |
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|---|---|
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| Step 1 — Command Interface | `Command.java` |
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| Step 2 — The Receiver (TextEditor) | `TextEditor.java` |
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| Step 3 — Concrete Commands | `InsertCommand.java`, `DeleteCommand.java` |
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| Step 4 — The Invoker (CommandHistory) | `CommandHistory.java` |
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| Demo | `Main.java` |
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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.
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Article: https://ankurm.com/command-design-pattern-java/
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All patterns: https://ankurm.com/design-patterns-java/
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