Enumeracions

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# Enumeracions

.footnote[Joan Puigcerver Ibáñez]

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# Enumeracions
- Tipus de dada que permet a una variable ser una constant predefinida d'un conjunt.
- Exmple:
  - Dia de la setmana
- Atenció: Ha de ser un conjunt tancat.

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# Enum

```
public enum DayOfWeek {
    SUNDAY, MONDAY, TUESDAY, WEDNESDAY,
    THURSDAY, FRIDAY, SATURDAY 
}
```

```
DayOfWeek dow = DayOfWeek.Monday;
```

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# Enum

```
public void tellItLikeItIs() {
    switch (day) {
        case MONDAY:
            System.out.println("Mondays are bad.");
            break;
        case FRIDAY:
            System.out.println("Fridays are better.");
            break;   
        case SATURDAY: case SUNDAY:
            System.out.println("Weekends are best.");
            break;
        default:
            System.out.println("Midweek days are so-so.");
            break;
    }
}
```

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# Enums
- Una enum pot tenir també atributs i funcions.

```
public enum SolarSystemPlanet {
  MERCURY (3.303e+23, 2.4397e6),
  VENUS   (4.869e+24, 6.0518e6),
  EARTH   (5.976e+24, 6.37814e6),
  MARS    (6.421e+23, 3.3972e6),
  JUPITER (1.9e+27,   7.1492e7),
  SATURN  (5.688e+26, 6.0268e7),
  URANUS  (8.686e+25, 2.5559e7),
  NEPTUNE (1.024e+26, 2.4746e7);

private final double mass;   // in kilograms
  private final double radius; // in meters
  Planet(double mass, double radius) {
      this.mass = mass;
      this.radius = radius;
  }
  public double getMass() { return mass; }
  public double getRadius() { return radius; }
}
```