add class GuavaFilterCollectionsTest
Test Example for article Guava - Predicates and Collections
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package org.baeldung.guava;
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import static org.junit.Assert.assertEquals;
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import java.util.Collection;
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import java.util.Collections;
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import java.util.List;
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import org.junit.Test;
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import com.google.common.base.Function;
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import com.google.common.base.Functions;
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import com.google.common.base.Predicate;
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import com.google.common.base.Predicates;
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import com.google.common.collect.Collections2;
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import com.google.common.collect.FluentIterable;
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import com.google.common.collect.ListMultimap;
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import com.google.common.collect.Lists;
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import com.google.common.collect.Multimaps;
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import com.google.common.collect.Ordering;
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public class GuavaFilterCollectionsTest {
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@Test
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public void whenFilterCollection_thenFiltered() {
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final List<String> names = Lists.newArrayList("John", "Jane", "Adam", "Tom");
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final Collection<String> result = Collections2.filter(names, Predicates.containsPattern("a"));
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assertEquals(2, result.size());
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assertEquals("[Jane, Adam]", result.toString());
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}
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@Test
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public void whenFilterCollectionWithCustomPredicate_thenFiltered() {
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final Predicate<String> predicate = new Predicate<String>() {
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@Override
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public final boolean apply(final String input) {
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return input.startsWith("A") || input.startsWith("J");
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}
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};
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final List<String> names = Lists.newArrayList("John", "Jane", "Adam", "Tom");
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final Collection<String> result = Collections2.filter(names, predicate);
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assertEquals(3, result.size());
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assertEquals("[John, Jane, Adam]", result.toString());
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}
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@Test
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public void whenFilterUsingMultiplePredicates_thenFiltered() {
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final List<String> names = Lists.newArrayList("John", "Jane", "Adam", "Tom");
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final Collection<String> result = Collections2.filter(names, Predicates.or(Predicates.containsPattern("J"), Predicates.not(Predicates.containsPattern("a"))));
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assertEquals(3, result.size());
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assertEquals("[John, Jane, Tom]", result.toString());
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}
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@Test
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public void whenTransformCollection_thenTransformed() {
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final Function<String, Integer> function = new Function<String, Integer>() {
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@Override
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public final Integer apply(final String input) {
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return input.length();
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}
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};
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final List<String> names = Lists.newArrayList("John", "Jane", "Adam", "Tom");
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final Collection<Integer> result = Collections2.transform(names, function);
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assertEquals(4, result.size());
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assertEquals("[4, 4, 4, 3]", result.toString());
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}
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@Test
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public void whenTransformUsingComposedFunction_thenTransformed() {
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final Function<String, Integer> f1 = new Function<String, Integer>() {
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@Override
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public final Integer apply(final String input) {
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return input.length();
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}
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};
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final Function<Integer, Boolean> f2 = new Function<Integer, Boolean>() {
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@Override
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public final Boolean apply(final Integer input) {
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return input % 2 == 0;
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}
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};
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final List<String> names = Lists.newArrayList("John", "Jane", "Adam", "Tom");
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final Collection<Boolean> result = Collections2.transform(names, Functions.compose(f2, f1));
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assertEquals(4, result.size());
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assertEquals("[true, true, true, false]", result.toString());
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}
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@Test
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public void whenFilterAndTransformCollection_thenCorrect() {
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final Predicate<String> predicate = new Predicate<String>() {
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@Override
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public final boolean apply(final String input) {
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return input.startsWith("A") || input.startsWith("T");
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}
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};
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final Function<String, Integer> func = new Function<String, Integer>() {
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@Override
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public final Integer apply(final String input) {
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return input.length();
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}
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};
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final List<String> names = Lists.newArrayList("John", "Jane", "Adam", "Tom");
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final Collection<Integer> result = FluentIterable.from(names).filter(predicate).transform(func).toList();
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assertEquals(2, result.size());
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assertEquals("[4, 3]", result.toString());
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}
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@Test
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public void whenSortCollection_thenSorted() {
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final List<String> names = Lists.newArrayList("John", "Jane", "Adam", "Tom");
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Collections.sort(names, Ordering.natural());
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assertEquals("[Adam, Jane, John, Tom]", names.toString());
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}
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@Test
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public void whenSortCollectionUsingCustomOrdering_thenSorted() {
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final Ordering<String> ordering = Ordering.natural().onResultOf(new Function<String, Integer>() {
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@Override
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public final Integer apply(final String input) {
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return input.length();
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}
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});
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final List<String> names = Lists.newArrayList("John", "Jane", "Adam", "Tom");
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Collections.sort(names, ordering);
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assertEquals("[Tom, John, Jane, Adam]", names.toString());
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}
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@Test
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public void whenGroupCollection_thenGrouped() {
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final List<String> names = Lists.newArrayList("John", "Jane", "Adam", "Tom");
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final ListMultimap<Integer, String> groups = Multimaps.index(names, new Function<String, Integer>() {
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@Override
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public final Integer apply(final String input) {
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return input.length();
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}
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});
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assertEquals(2, groups.keySet().size());
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assertEquals(3, groups.get(4).size());
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assertEquals("[Tom]", groups.get(3).toString());
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}
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}
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