## Singleton

### Instructions

In this quest, we will implement some design patterns.

For first, we will implement the singleton pattern.

```mermaid
classDiagram
class Excalibur{
    -String name
    -Excalibur INSTANCE$
    -Excalibur(String name)
    +getName() String
    +getInstance()$ Excalibur
}
Excalibur <-- Excalibur
```

Here is the matching class diagram. Create the matching class in the matching file.

When calling the getInstance method, an instance of Excalibur with name "Sword"

### Usage

Here is a possible ExerciseRunner.java to test your function :

```java
public class ExerciseRunner {

    public static void main(String[] args)  {
        System.out.println(Excalibur.getInstance().getName());
    }
}
```
          
and its output :
```shell
$ javac *.java -d build
$ java -cp build ExerciseRunner 
Sword
$
```

### Notions
[Class diagram](https://fr.wikipedia.org/wiki/Diagramme_de_classes)