CODEWITHSUNDEEP
javaeclipsenullpointerexceptionlombok
D V Santhosh Kiran
D V Santhosh Kiran

Reputation: 159

How to handle null values in Java (eclipse IDE)

I'm working on an API (Eclipse IDE - Kepler), JDK 1.7) I need a shortcut like @IfNotNullUpdate

consider the following e.g. 

Model model = new Model();
String field1 = entity.getField1() != null ? entity.getField1() : "";
model.setField1(field1);

so that I can simply write it like

model.setField1( @IfNotNullUpdate entity.getField1(),"");

I don't want to have any NullPointerExceptions. It will be a great help If it can work like builder pattern. for e.g.

model.addField_25(@IfNotNullUpdate entity.getField_37())
     .addField_16(@IfNotNullUpdate entity.getField_69());

I tried @NonNull of lombok. It just ensures that param is not null which is not my requirement.

And of-course assert() can't be a solution. Hope I'm able to explain my requirement well.

Thanks in advance.

Upvotes: 0

Views: 1247

Answers (4)

D V Santhosh Kiran
D V Santhosh Kiran

Reputation: 159

Updating answer with JDK17:

I have a helper method like

public class NpeHelper {
 public static <T> Optional<T> ofNullable(final Supplier<T> resolver) {
        try {
            final T result = resolver.get();
            return Optional.ofNullable(result);
        } catch (NullPointerException e) {
            return Optional.empty();
        }
    }
}

I can use this helper function as

model.addField_25(NpeHelper.ofNullable(()-> entity.getField_37()).orElse(<AnyObject<));

For Nullable streams validation I'm using ApacheCommons' CollectionUtils.emptyIfNull();

Upvotes: 0

M. Shaw
M. Shaw

Reputation: 1742

Have a look at Optional. Using the sample provided, the following can throw a NPE if any of the methods called returns a null value:

String version = computer.getSoundcard().getUSB().getVersion();

To avoid that or excessive if (x != null) checks, using Optional you can use:

String name = computer.flatMap(Computer::getSoundcard)
                          .flatMap(Soundcard::getUSB)
                          .map(USB::getVersion)
                          .orElse("UNKNOWN");

Upvotes: 1

rone
rone

Reputation: 67

Why don't you use just a method? You can make it static if you want, so that you can access it by className. Or put your helper methods that you need in oneClass and extend it. 

public String getFieldValue(Object o ){
    if(o instanceof someEntity){
        someEntity se = (someEntity) o
        if(someEntity.getField() != null){
            return someEntity.getField();
        }else{
            return ""; 
        }
    }else if(o instanceof someOtherEntity){
       ...
    }
}

Upvotes: 0

Karthik R
Karthik R

Reputation: 5786

You would need to build a custom annotation for this or any purpose of yours. You can create an Annotation for you with @Target(ElementType.PARAMETER) and sue reflection to map it as required. But this is so lengthy process which doesn't need much of your time. Instead just write a method and just call it.

I can't think of an API readily available. As you pointed out, lombok doesn't do that for you.

Upvotes: 0

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