@Override
    public boolean equals(Object obj) {
        
        if(obj == null){
            return false;
        }
        
        if (this == obj){
            return true;
        }
        
        if( ! (obj instanceof Data)){
            return false;
        }
        
        Data d = (Data) obj;
        
        return this.dia == d.dia && this.mes == d.mes && this.ano == d.ano; 
    }
    
    @Override
    public int hashCode() {
        int r = 17;
        r = 31 * r + this.dia;
        r = 31 * r + this.mes;
        r = 31 * r + this.ano;
        return r;
    }