> 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/mapas.md).

# Mapas

```java
public class EntradaMapa<K, V> {

    private K chave;
    private V valor;

    public EntradaMapa(K chave, V valor) {
        this.chave = chave;
        this.valor = valor;
    }

    public K getChave() {
        return chave;
    }

    public void setChave(K chave) {
        this.chave = chave;
    }

    public V getValor() {
        return valor;
    }

    public void setValor(V valor) {
        this.valor = valor;
    }

    @Override
    public String toString() {
        return chave + " = " + valor;
    }
}
```

```java
public class Mapa<K, V> {

    private EntradaMapa<K, V>[] entradas;

    public Mapa() {
        entradas = new EntradaMapa[10];
    }

    private int getIndice(K chave) {
        return Math.abs(chave.hashCode() % CAPACIDADE);
    }

    public void put(K chave, V valor) {
        int indice = getIndice(chave);
        EntradaMapa<K, V> novaEntrada = new EntradaMapa<>(chave, valor);

        if (entradas[indice] == null) {
            entradas[indice] = novaEntrada;
        } else {
            if (entradas[indice].getChave().equals(chave)) {
                entradas[indice].setValor(valor);
            } else {
                System.out.println("Non foi posible a inserción, " +
                        "houbo unha colisión na posición " + indice);
            }
        }
    }

    public V get(K chave) {
        int indice = getIndice(chave);
        EntradaMapa<K, V> entrada = entradas[indice];

        if (entrada != null && entrada.getChave().equals(chave)) {
            return entrada.getValor();
        }
        return null;
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder("Mapa {\n");
        for (EntradaMapa<K, V> entrada : entradas) {
            if (entrada != null) {
                sb.append("  [").append(entrada).append("]\n");
            }
        }
        sb.append("}");
        return sb.toString();
    }
}
```

```java
public class App {

    public static void main(String[] args) {

        Mapa<String, Integer> mapa = new Mapa<>();

        // Insercións normais
        mapa.put("casa", 15);
        mapa.put("can", 4);
        mapa.put("gato", 7);
        mapa.put("paxaro", 2);
        System.out.println("Após insercións iniciais:");
        System.out.println(mapa);

        // Recuperación de valores
        System.out.println("Valor de 'casa': " + mapa.get("casa"));
        System.out.println("Valor de 'can':  " + mapa.get("can"));
        System.out.println("Valor de 'rato' (non existe): " + mapa.get("rato"));

        // Actualización dun valor existente
        System.out.println("\nActualizando 'casa' a 99...");
        mapa.put("casa", 99);
        System.out.println("Valor de 'casa' tras actualizar: " + mapa.get("casa"));

        // Forza unha colisión manual: buscamos dúas chaves co mesmo índice
        // hashCode("Aa") == hashCode("BB") en Java → mesma posición no array
        System.out.println("\nProbando colisión:");
        mapa.put("Aa", 100);
        mapa.put("BB", 200); // colisión con "Aa"
    }
}
```


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