Java. Function with possibly throwable params (NullpointerException)?

Question

When I have a number of expressions that can throw an exception, for example:

instanceObj.final_doc_type = instance.getFinalDocument().getValue().getType().getVa         


        

Answer 1

Use Optional.map:

instanceObj.final_doc_type = 
    Optional.ofNullable(instance)
      .map(Instance::getFinalDocument)
      .map(Document::getValue)
      .map(Value::getType)
      .map(Type::getValue)
      .orElse(null);

This sets final_doc_type to null if anything in the chain is null.

If you only want to set its value in the case of a non-null value, remove the assignment, and change the orElse to ifPresent:

Optional.ofNullable(instance)
    /* ... */
    .ifPresent(t -> instanceObj.final_doc_type = t);