code: @Override
      public JFieldVar apply(String nodeName, JsonNode node, JsonNode parent, JFieldVar field, Schema currentSchema) {
  
          boolean defaultPresent = node != null && isNotEmpty(node.asText());
  
          String fieldType = field.type().fullName();
  
          if (defaultPresent && !field.type().isPrimitive() && node.isNull()) {
              field.init(JExpr._null());
  
          } else if (fieldType.startsWith(List.class.getName())) {
              field.init(getDefaultList(field.type(), node));
  
          } else if (fieldType.startsWith(Set.class.getName())) {
              field.init(getDefaultSet(field.type(), node));
          } else if (fieldType.startsWith(String.class.getName()) && node != null ) {
              field.init(getDefaultValue(field.type(), node));
          } else if (defaultPresent) {
              field.init(getDefaultValue(field.type(), node));
  
          }
  
          return field;
      }
docs: Applies this schema rule to take the required code generation steps.
  <p>
  Default values are implemented by assigning an expression to the given
  field (so when instances of the generated POJO are created, its fields
  will then contain their default values).
  <p>
  Collections (Lists and Sets) are initialized to an empty collection, even
  when no default value is present in the schema (node is null).
  
  @param nodeName
  the name of the property which has (or may have) a default
  @param node
  the default node (may be null if no default node was present
  for this property)
  @param field
  the Java field that has added to a generated type to represent
  this property
  @return field, which will have an init expression is appropriate