泛型实现的简单KeyAndValue

public class KeyAndValue<K, V> implements Serializable {    private K key;    private V value;    public KeyAndValue() {    }    public KeyAndValue(K k, V v) {        this.key = k;        this.value = v;    }    public K getKey() {        return this.key;    }    public void setKey(K key) {        this.key = key;    }    public V getValue() {        return this.value;    }    public void setValue(V value) {        this.value = value;    }}