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The **Mediator** pattern reduces coupling between objects by **replacing direct links between them with a single point of interaction**, a centralized mediator.

---

### 1. **Without a Mediator, a Full Mesh of Dependencies**

If objects interact directly, each one has to **know about the others**:
who exists in the system, what methods they have, when to call them.

> Example:
> In a registration window, the `Email` field tells the `Login` button when to activate,
> and the button, in turn, calls `PasswordField` methods for validation.

The result is a **"web-like architecture"**, where changing one component requires edits everywhere else.

---

### 2. **With a Mediator, All Links Go Through One Object**

Each component only knows **one participant**, the *mediator*:

```java
class Button {
    private Mediator mediator;
    public void click() {
        mediator.notify(this, "click");
    }
}
```

The mediator receives events from components and decides **who should react**:

```java
class DialogMediator implements Mediator {
    private Button loginButton;
    private TextBox emailField;
    private TextBox passwordField;

public void notify(Component sender, String event) {
        if (sender == emailField || sender == passwordField)
            loginButton.setEnabled(!emailField.isEmpty() && !passwordField.isEmpty());
    }
}
```

Now `EmailField`, `PasswordField`, and `Button` **don't know about each other**,
they simply "report the news" to the mediator.

---

### 3. **What This Gives You**

- **Weaker coupling**, each object knows only the Mediator,
not dozens of other components.
- **Easy modification**, a new component can be added without changing the others.
- **Reusability**, components become independent and can be used in other contexts.
- **Simplified interaction logic**, all the behavior between objects is now concentrated in one place.

---

### 4. **Analogy**

Without Mediator, it's as if every airplane pilot communicated directly with every other pilot.
With Mediator, all pilots talk only to the **dispatcher**,
and the dispatcher decides who should act and when.

---

### **Conclusion**

The **Mediator** pattern reduces coupling because it:

- replaces **many direct links with one central one**,
- makes components **independent and reusable**,
- concentrates interaction in one place,
simplifying maintenance and the evolution of the system.

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