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**Command** is a **behavioral pattern** that turns a **request or action into a separate object**, encapsulating all the information needed to execute it.

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### 1. **The Core Idea**

Instead of calling methods directly, the program creates a command object that stores:

- a reference to the receiver (the object that will perform the action),
- the action itself,
- and the parameters it needs.

Such an object can be **passed around, queued, canceled, or repeated** - all without knowing how the operation is actually performed.

> **Idea:** "pack an action into an object".

---

### 2. **Why It's Needed**

- To **decouple a request from its executor**.
- To be able to **delay execution**, **queue**, or **cancel** an action.
- To implement an **operation history**, macros, "undo/redo", transactions.

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### 3. **Structure**

- **Command** - an interface with an `execute()` method.
- **ConcreteCommand** - a specific command that calls the needed method on the receiver.
- **Receiver** - the object that knows how to perform the action.
- **Invoker** - the initiator that triggers the command (for example, a button).
- **Client** - creates the command and passes it to the invoker.

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### 4. **Example (Java)**

```java
interface Command {
    void execute();
}

class Light {
    void turnOn() { System.out.println("Light turned on"); }
    void turnOff() { System.out.println("Light turned off"); }
}

class TurnOnCommand implements Command {
    private Light light;
    public TurnOnCommand(Light light) { this.light = light; }
    public void execute() { light.turnOn(); }
}

class RemoteControl {
    private Command command;
    public void setCommand(Command command) { this.command = command; }
    public void pressButton() { command.execute(); }
}

// Usage
Light light = new Light();
Command on = new TurnOnCommand(light);
RemoteControl remote = new RemoteControl();
remote.setCommand(on);
remote.pressButton();
```

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### 5. **Advantages**

- Allows you to **decouple the client from the execution logic**.
- Supports **queues, history, undo/redo**.
- Simplifies adding new commands without changing existing code.
- Fits **GUI buttons, menus, task schedulers**.

---

### **Conclusion**

**Command** is needed to represent an action as an **object** that can be **executed, undone, logged, and combined**,
thereby making the system **flexible, extensible, and controllable over time**.

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