Demonstrate mapping and filtering using Java 7, Guava, and Java 8 constructs.

MapFilterTest.java

/**
 * Demonstrate mapping and filtering using Java 7, Guava, and Java 8 constructs.
 *
 * Test with:
 * javac -cp .:$HOME/.m2/repository/com/google/guava/guava/15.0/guava-15.0.jar MapFilterTest.java
 */

import java.util.Collection;
import java.util.Iterator;

import com.google.common.base.Function;
import com.google.common.base.Functions;
import com.google.common.base.Predicate;
import com.google.common.base.Predicates;
import com.google.common.collect.FluentIterable;
import com.google.common.collect.Lists;

public class MapFilterTest {
    /** Java 7 imperative style. */
    private static Iterator<String> testImperative(
            Collection<Object> objects) {
        Collection<String> strings = Lists.newArrayList();
        for (Object object : objects) {
            if (object != null) {
                strings.add(object.toString());
            }
        }
        return strings.iterator();
    }

    /** Guava functional programming (without helpers). */
    private static Iterator<String> testFluentIterable(
            Collection<Object> objects) {
        return FluentIterable.from(objects)
                .filter(new Predicate<Object>() {
                    @Override
                    public boolean apply(Object object) {
                        return object != null;
                    }
                }).transform(new Function<Object, String>() {
                    @Override
                    public String apply(Object object) {
                        return object.toString();
                    }
                }).iterator();
    }

    /** Guava functional programming (with helpers). */
    private static Iterator<String> testFluentIterableWithHelpers(
            Collection<Object> objects) {
        return FluentIterable.from(objects)
                .filter(Predicates.notNull())
                .transform(Functions.toStringFunction())
                .iterator();
    }

    /** Java 8 functional style. */
    private static Iterator<String> testLambda(
            Collection<Object> objects) {
        return objects.stream()
                .filter(object -> object != null)
                .map(Object::toString)
                .iterator();
    }
}