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functional examples

This commit is contained in:
Eugen Paraschiv 2013-10-30 12:18:46 +02:00
parent 6af58dce94
commit b97de291f1
1 changed files with 65 additions and 3 deletions
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68
guava/src/test/java/org/baeldung/guava/GuavaFunctionalExamplesTest.java
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@ -1,11 +1,14 @@
package org.baeldung.guava;
import static org.hamcrest.Matchers.contains;
import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.Matchers.lessThan;
import static org.junit.Assert.assertThat;
import static org.junit.Assert.assertTrue;
import java.util.Arrays;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
@ -13,18 +16,21 @@ import java.util.Set;
import org.junit.Test;
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.Collections2;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.collect.Ordering;
import com.google.common.collect.Sets;
public class GuavaFunctionalExamplesTest {
// tests
// predicates
// predicates - filtering
@Test
public final void whenFilteringNumbersAccordingToACondition_thenCorrectResults() {
@ -41,9 +47,19 @@ public class GuavaFunctionalExamplesTest {
assertThat(found, lessThan(0));
}
@Test
public final void givenCollectionContainsNulls_whenNullsAreFilteredOut_thenResultingCollectionsHasNoNulls() {
final List<String> collectionOfStringsWithNulls = Lists.newArrayList("a", "bc", null, "def", null, null, "ghij");
final Iterable<String> collectionWithoutNulls = Iterables.filter(collectionOfStringsWithNulls, Predicates.notNull());
assertTrue(Iterables.all(collectionWithoutNulls, Predicates.notNull()));
}
// predicates - checking
@Test
public final void givenEvenNumbers_whenCheckingIfAllSatisfyTheEvenPredicate_thenYes() {
final List<Integer> eventNumbers = Lists.newArrayList(2, 6, 8, 10, 34, 90);
final List<Integer> evenNumbers = Lists.newArrayList(2, 6, 8, 10, 34, 90);
final Predicate<Integer> acceptEvenNumber = new Predicate<Integer>() {
@Override
public final boolean apply(final Integer number) {
@ -51,7 +67,53 @@ public class GuavaFunctionalExamplesTest {
}
};
assertTrue(Iterables.all(eventNumbers, acceptEvenNumber));
assertTrue(Iterables.all(evenNumbers, acceptEvenNumber));
}
// negating a predicate
@Test
public final void givenCollectionOfEvenNumbers_whenCheckingThatCollectionContainsNoOddNumber_thenTrue() {
final List<Integer> evenNumbers = Lists.newArrayList(2, 6, 8, 10, 34, 90);
final Predicate<Integer> acceptEvenNumber = new Predicate<Integer>() {
@Override
public final boolean apply(final Integer number) {
return (number % 2) != 0;
}
};
assertTrue(Iterables.all(evenNumbers, Predicates.not(acceptEvenNumber)));
}
// try - 1
@Test(expected = UnsupportedOperationException.class)
public final void givenUnmodifiableViewOverIterable_whenTryingToRemove_thenNotAllowed() {
final List<Integer> numbers = Lists.newArrayList(1, 2, 3);
final Iterable<Integer> unmodifiableIterable = Iterables.unmodifiableIterable(numbers);
final Iterator<Integer> iterator = unmodifiableIterable.iterator();
if (iterator.hasNext()) {
iterator.remove();
}
}
// functions
@Test
public final void whenApplyingSimpleFunctionToInputs_thenCorrectlyTransformed() {
final List<Integer> numbers = Lists.newArrayList(1, 2, 3);
final List<String> numbersAsStrings = Lists.transform(numbers, Functions.toStringFunction());
assertThat(numbersAsStrings, contains("1", "2", "3"));
}
@Test
public final void whenUsingAnIntermediaryFunctionToOrder_thenCorerctlyOrderedInAlphabeticalOrder() {
final List<Integer> numbersToSort = Arrays.asList(2, 1, 11, 100, 8, 14);
final Ordering<Object> ordering = Ordering.natural().onResultOf(Functions.toStringFunction());
final List<Integer> alphabeticalOrderingOfNumbers = ordering.sortedCopy(numbersToSort);
final List<Integer> expectedAlphabeticalOrderingOfNumbers = Lists.newArrayList(1, 100, 11, 14, 2, 8);
assertThat(expectedAlphabeticalOrderingOfNumbers, equalTo(alphabeticalOrderingOfNumbers));
}
// Set+Function => Map