Java 8 Lambda for Anonymous Class

Question

I have a tricky situation here, which I would like to optimize from the code perspective. Is there any way to shorten the following method via Lambda / Java8 expressions?

// total amount of audiences
registry.register("metric.persons.total", new CachedGauge<Integer>(1,TimeUnit.MINUTES) {
    @Override
    protected Integer loadValue() {
        return personService.findAll().size();
    }
});

The CachedGauge class is looking like this:

public abstract class CachedGauge<T> implements Gauge<T> {
    protected CachedGauge(long timeout, TimeUnit timeoutUnit) {
        ...
    }

    protected abstract T loadValue();
        ...
    }
}

Would be really great to see if there is a way, the tricky part here is that there is a default constructor and the class is parameterized.

best, fri

Does personService come from the anonymous class's containing scope, or is it a public/protected field inherited from CachedGauge? — ruakh
– ruakh, Commented May 29, 2015 at 23:28
ah sorry... the person service is a protected field in the outer class, similar to the "registry" object — Fritz
– Fritz, Commented May 29, 2015 at 23:31

ZhongYu · Accepted Answer · 2015-05-29 23:31:41Z

5

registry.register("metric.persons.total", 
    CachedGauge.of(1,TimeUnit.MINUTES, ()->personService.findAll().size() ) 
);

And I think you can figure out how to implement CachedGauge.of(long, TimeUnit, Supplier<T>)

answered May 29, 2015 at 23:31

ZhongYu

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2 Comments

Fritz Over a year ago

Thanks, this looks good. Problem is, that the CachedGauge is 3rd party class, which I tried not to override... But I then create my own Utils class...

ZhongYu Over a year ago

@Fritz - exactly. It's a util method that can be put anywhere.

Fritz · Accepted Answer · 2015-05-29 23:49:08Z

1

Just for completion of this thread, my Utils class looks like this

public class MetricUtils {

    public static <T> CachedGauge<T> cachedGauge(long timeout, TimeUnit timeoutUnit, Supplier<T> supplier) {
        return new CachedGauge<T>(timeout, timeoutUnit) {
            @Override
            protected T loadValue() {
                return supplier.get();
            }
        };
    }
}

answered May 29, 2015 at 23:49

Fritz

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