如何将参数化的匿名类转换为lambda？

Question

I want to refactor my code (Sonar also wants me to do that :) ).

I should use a lambda instead of an anonymous class.

I have the following code:

@Component
public class InsuranceValidateRespDataToDtoMapper extends PropertyMapConfigurerSupport<InsuranceValidateResponseData,
        com.package.InsuranceValidateResponseData> {

    @Override
    public PropertyMap<InsuranceValidateResponseData, com.package.InsuranceValidateResponseData> mapping() {
        return new PropertyMap<InsuranceValidateResponseData, com.package.InsuranceValidateResponseData>() {
            @Override
            protected void configure() {
                using(BIG_DECIMAL_TO_INTEGER_AMOUNT_CONVERTER).map(source.getLackCurr()).setLackCurr(null);
                using(BIG_DECIMAL_TO_INTEGER_AMOUNT_CONVERTER).map(source.getLackEur()).setLackEur(null);
            }
        };
    }
}

When I make the following change, the code won't compile.

@Component
public class InsuranceValidateRespDataToDtoMapper extends PropertyMapConfigurerSupport<InsuranceValidateResponseData,
        com.package.InsuranceValidateResponseData> {

    @Override
    public PropertyMap<InsuranceValidateResponseData, com.package.InsuranceValidateResponseData> mapping() {
        return () -> {
            using(BIG_DECIMAL_TO_INTEGER_AMOUNT_CONVERTER).map(source.getLackCurr()).setLackCurr(null);
            using(BIG_DECIMAL_TO_INTEGER_AMOUNT_CONVERTER).map(source.getLackEur()).setLackEur(null);
        };
    }
}

Compilation fails because it can't resolve "using" and "source"

Answer 1

Here:

return new PropertyMap<InsuranceValidateResponseData, com.package.InsuranceValidateResponseData>() {
return () -> {
        using(BIG_DECIMAL_TO_INTEGER_AMOUNT_CONVERTER).map(source.getLackCurr()).setLackCurr(null);
        using(BIG_DECIMAL_TO_INTEGER_AMOUNT_CONVERTER).map(source.getLackEur()).setLackEur(null);
    };
}

There are two returns in there - doesn't make sense; go for that second

return -> { ... }

only; and remove the other stuff that you have in front of it!

But the more important aspect here: don't do things blindly because some tool tells you so.

Instead: step back; understand what the tool is telling you (like: what are the options; and do you really buy into "that other option is better than what you have right now"). Sure, if everybody agrees on "we want 0 SonarQube warnings", then that is what you could do. On the other hand; when touching code; as said: don't do it blindly. Maybe you can step back; and even do a better refactoring here.

(I am not saying that this is possible here; I am just pointing out: when you are touching your code; make sure that the change you will commit makes really sense to you).

Answer 2

Try rewriting your method like this, if your PropertyMap is functional interface

@Override
public PropertyMap<InsuranceValidateResponseData, com.package.InsuranceValidateResponseData> mapping() {
    return () -> {
        using(BIG_DECIMAL_TO_INTEGER_AMOUNT_CONVERTER).map(source.getLackCurr()).setLackCurr(null);
        using(BIG_DECIMAL_TO_INTEGER_AMOUNT_CONVERTER).map(source.getLackEur()).setLackEur(null);
    };
}

Functional interfaces can be represented like lambda-functions, and in this case you only need to write a lambda-function for that single method from functional interface. Simple example with BiConsumer class :

BiConsumer<String, String> getConsumer() {
    return new BiConsumer<String, String>() {
        @Override
        public void accept(String s, String s2) {
            // accept strings
        }
    };
}

Can be represented as lambda-function with specifying only accept method:

BiConsumer<String, String> getConsumer() {
    return (s, s2) -> {
        // accept strings
    };
}