> For the complete documentation index, see [llms.txt](https://educacion.gitbook.io/programacion/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://educacion.gitbook.io/programacion/exercicios-java/ud6-solucions/conxuntos-set-e-hashset.md).

# Conxuntos: Set e HashSet

```java
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class GrupoAlumnos {

    private Set<String> alumnos;

    public GrupoAlumnos(List<String> alumnos) {
        this.alumnos = new HashSet<>(alumnos);
    }

    private GrupoAlumnos(Set<String> alumnos) {
        this.alumnos = alumnos;
    }

    public void engadir(String alumno) {
        alumnos.add(alumno);
    }

    public void eliminar(String alumno) {
        alumnos.remove(alumno);
    }

    public boolean contains(String alumno) {
        return alumnos.contains(alumno);
    }

    public GrupoAlumnos union(GrupoAlumnos outro) {
        Set<String> resultado = new HashSet<>(this.alumnos);
        resultado.addAll(outro.alumnos);
        return new GrupoAlumnos(resultado);
    }

    public GrupoAlumnos interseccion(GrupoAlumnos outro) {
        Set<String> resultado = new HashSet<>(this.alumnos);
        resultado.retainAll(outro.alumnos);
        return new GrupoAlumnos(resultado);
    }

    @Override
    public String toString() {
        return "GrupoAlumnos{" + "alumnos=" + alumnos + '}';
    }
}
```

```java
import java.util.Arrays;
import java.util.List;

public class App {
    public static void main(String[] args) {

        List<String> listaA = Arrays.asList("Ana", "Carlos", "Marta", "Xoan");
        List<String> listaB = Arrays.asList("María", "Jorge", "Lucía", "David");

        GrupoAlumnos grupoA = new GrupoAlumnos(listaA);
        GrupoAlumnos grupoB = new GrupoAlumnos(listaB);

        // Engadir
        grupoA.engadir("Luís");
        grupoA.engadir("Ana"); // Duplicado, non se engade
        System.out.println("GrupoA: " + grupoA);

        // Eliminar
        grupoA.eliminar("Carlos");
        System.out.println("GrupoA sen Carlos: " + grupoA);

        // Contains
        System.out.println("Marta está en grupoA: " + grupoA.contains("Marta"));
        System.out.println("Carlos está en grupoA: " + grupoA.contains("Carlos"));

        // Unión
        GrupoAlumnos union = grupoA.union(grupoB);
        System.out.println("Unión: " + union);

        // Intersección (grupos sen alumnos comúns)
        GrupoAlumnos interseccion = grupoA.interseccion(grupoB);
        System.out.println("Intersección: " + interseccion);
    }
}
```


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