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Java example source code file (Collections2Test.java)

This example Java source code file (Collections2Test.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

collection, expected, gwtincompatible, iterator, length_1, list, nosuchelementexception, not_yyy_zzz, nullpointertester, override, predicate, remove_first_char, test, teststringcollectiongenerator, util

The Collections2Test.java Java example source code

/*
 * Copyright (C) 2008 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.collect.Iterables.concat;
import static com.google.common.collect.Lists.newArrayList;
import static com.google.common.collect.Lists.newLinkedList;
import static com.google.common.truth.Truth.assertThat;
import static java.util.Arrays.asList;
import static java.util.Collections.nCopies;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.base.Function;
import com.google.common.base.Predicate;
import com.google.common.collect.testing.CollectionTestSuiteBuilder;
import com.google.common.collect.testing.TestStringCollectionGenerator;
import com.google.common.collect.testing.features.CollectionFeature;
import com.google.common.collect.testing.features.CollectionSize;
import com.google.common.testing.NullPointerTester;

import junit.framework.Test;
import junit.framework.TestCase;
import junit.framework.TestSuite;

import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;

/**
 * Tests for {@link Collections2}.
 *
 * @author Chris Povirk
 * @author Jared Levy
 */
@GwtCompatible(emulated = true)
public class Collections2Test extends TestCase {
  @GwtIncompatible // suite
  public static Test suite() {
    TestSuite suite = new TestSuite(Collections2Test.class.getSimpleName());
    suite.addTest(testsForFilter());
    suite.addTest(testsForFilterAll());
    suite.addTest(testsForFilterLinkedList());
    suite.addTest(testsForFilterNoNulls());
    suite.addTest(testsForFilterFiltered());
    suite.addTest(testsForTransform());
    suite.addTestSuite(Collections2Test.class);
    return suite;
  }

  static final Predicate<String> NOT_YYY_ZZZ = new Predicate() {
      @Override
      public boolean apply(String input) {
        return !"yyy".equals(input) && !"zzz".equals(input);
      }
  };

  static final Predicate<String> LENGTH_1 = new Predicate() {
    @Override
    public boolean apply(String input) {
      return input.length() == 1;
    }
  };

  static final Predicate<String> STARTS_WITH_VOWEL = new Predicate() {
    @Override
    public boolean apply(String input) {
      return asList('a', 'e', 'i', 'o', 'u').contains(input.charAt(0));
    }
  };

  @GwtIncompatible // suite
  private static Test testsForFilter() {
    return CollectionTestSuiteBuilder.using(
        new TestStringCollectionGenerator() {
          @Override public Collection<String> create(String[] elements) {
            List<String> unfiltered = newArrayList();
            unfiltered.add("yyy");
            Collections.addAll(unfiltered, elements);
            unfiltered.add("zzz");
            return Collections2.filter(unfiltered, NOT_YYY_ZZZ);
          }
        })
        .named("Collections2.filter")
        .withFeatures(
            CollectionFeature.SUPPORTS_ADD,
            CollectionFeature.SUPPORTS_REMOVE,
            CollectionFeature.ALLOWS_NULL_VALUES,
            CollectionFeature.KNOWN_ORDER,
            CollectionSize.ANY)
        .createTestSuite();
  }

  @GwtIncompatible // suite
  private static Test testsForFilterAll() {
    return CollectionTestSuiteBuilder.using(
        new TestStringCollectionGenerator() {
          @Override public Collection<String> create(String[] elements) {
            List<String> unfiltered = newArrayList();
            Collections.addAll(unfiltered, elements);
            return Collections2.filter(unfiltered, NOT_YYY_ZZZ);
          }
        })
        .named("Collections2.filter")
        .withFeatures(
            CollectionFeature.SUPPORTS_ADD,
            CollectionFeature.SUPPORTS_REMOVE,
            CollectionFeature.ALLOWS_NULL_VALUES,
            CollectionFeature.KNOWN_ORDER,
            CollectionSize.ANY)
        .createTestSuite();
  }

  @GwtIncompatible // suite
  private static Test testsForFilterLinkedList() {
    return CollectionTestSuiteBuilder.using(
        new TestStringCollectionGenerator() {
          @Override public Collection<String> create(String[] elements) {
            List<String> unfiltered = newLinkedList();
            unfiltered.add("yyy");
            Collections.addAll(unfiltered, elements);
            unfiltered.add("zzz");
            return Collections2.filter(unfiltered, NOT_YYY_ZZZ);
          }
        })
        .named("Collections2.filter")
        .withFeatures(
            CollectionFeature.SUPPORTS_ADD,
            CollectionFeature.SUPPORTS_REMOVE,
            CollectionFeature.ALLOWS_NULL_VALUES,
            CollectionFeature.KNOWN_ORDER,
            CollectionSize.ANY)
        .createTestSuite();
  }

  @GwtIncompatible // suite
  private static Test testsForFilterNoNulls() {
    return CollectionTestSuiteBuilder.using(
        new TestStringCollectionGenerator() {
          @Override public Collection<String> create(String[] elements) {
            List<String> unfiltered = newArrayList();
            unfiltered.add("yyy");
            unfiltered.addAll(ImmutableList.copyOf(elements));
            unfiltered.add("zzz");
            return Collections2.filter(unfiltered, LENGTH_1);
          }
        })
        .named("Collections2.filter, no nulls")
        .withFeatures(
            CollectionFeature.SUPPORTS_ADD,
            CollectionFeature.SUPPORTS_REMOVE,
            CollectionFeature.ALLOWS_NULL_QUERIES,
            CollectionFeature.KNOWN_ORDER,
            CollectionSize.ANY)
        .createTestSuite();
  }

  @GwtIncompatible // suite
  private static Test testsForFilterFiltered() {
    return CollectionTestSuiteBuilder.using(
        new TestStringCollectionGenerator() {
          @Override public Collection<String> create(String[] elements) {
            List<String> unfiltered = newArrayList();
            unfiltered.add("yyy");
            unfiltered.addAll(ImmutableList.copyOf(elements));
            unfiltered.add("zzz");
            unfiltered.add("abc");
            return Collections2.filter(
                Collections2.filter(unfiltered, LENGTH_1), NOT_YYY_ZZZ);
          }
        })
        .named("Collections2.filter, filtered input")
        .withFeatures(
            CollectionFeature.SUPPORTS_ADD,
            CollectionFeature.SUPPORTS_REMOVE,
            CollectionFeature.KNOWN_ORDER,
            CollectionFeature.ALLOWS_NULL_QUERIES,
            CollectionSize.ANY)
        .createTestSuite();
  }

  private static final Function<String, String> REMOVE_FIRST_CHAR
      = new Function<String, String>() {
        @Override
        public String apply(String from) {
          return ((from == null) || "".equals(from))
              ? null : from.substring(1);
        }
      };

  @GwtIncompatible // suite
  private static Test testsForTransform() {
    return CollectionTestSuiteBuilder.using(
        new TestStringCollectionGenerator() {
          @Override public Collection<String> create(String[] elements) {
            List<String> list = newArrayList();
            for (String element : elements) {
              list.add((element == null) ? null : "q" + element);
            }
            return Collections2.transform(list, REMOVE_FIRST_CHAR);
          }
        })
        .named("Collections2.transform")
        .withFeatures(
            CollectionFeature.REMOVE_OPERATIONS,
            CollectionFeature.ALLOWS_NULL_VALUES,
            CollectionFeature.KNOWN_ORDER,
            CollectionSize.ANY)
        .createTestSuite();
  }

  @GwtIncompatible // NullPointerTester
  public void testNullPointerExceptions() {
    NullPointerTester tester = new NullPointerTester();
    tester.testAllPublicStaticMethods(Collections2.class);
  }

  public void testOrderedPermutationSetEmpty() {
    List<Integer> list = newArrayList();
    Collection<List permutationSet =
        Collections2.orderedPermutations(list);

    assertEquals(1, permutationSet.size());
    assertThat(permutationSet).contains(list);

    Iterator<List permutations = permutationSet.iterator();

    assertNextPermutation(Lists.<Integer>newArrayList(), permutations);
    assertNoMorePermutations(permutations);
  }

  public void testOrderedPermutationSetOneElement() {
    List<Integer> list = newArrayList(1);
    Iterator<List permutations =
        Collections2.orderedPermutations(list).iterator();

    assertNextPermutation(newArrayList(1), permutations);
    assertNoMorePermutations(permutations);
  }

  public void testOrderedPermutationSetThreeElements() {
    List<String> list = newArrayList("b", "a", "c");
    Iterator<List permutations =
        Collections2.orderedPermutations(list).iterator();

    assertNextPermutation(newArrayList("a", "b", "c"), permutations);
    assertNextPermutation(newArrayList("a", "c", "b"), permutations);
    assertNextPermutation(newArrayList("b", "a", "c"), permutations);
    assertNextPermutation(newArrayList("b", "c", "a"), permutations);
    assertNextPermutation(newArrayList("c", "a", "b"), permutations);
    assertNextPermutation(newArrayList("c", "b", "a"), permutations);
    assertNoMorePermutations(permutations);
  }

  public void testOrderedPermutationSetRepeatedElements() {
    List<Integer> list = newArrayList(1, 1, 2, 2);
    Iterator<List permutations =
        Collections2.orderedPermutations(list, Ordering.natural()).iterator();

    assertNextPermutation(newArrayList(1, 1, 2, 2), permutations);
    assertNextPermutation(newArrayList(1, 2, 1, 2), permutations);
    assertNextPermutation(newArrayList(1, 2, 2, 1), permutations);
    assertNextPermutation(newArrayList(2, 1, 1, 2), permutations);
    assertNextPermutation(newArrayList(2, 1, 2, 1), permutations);
    assertNextPermutation(newArrayList(2, 2, 1, 1), permutations);
    assertNoMorePermutations(permutations);
  }

  public void testOrderedPermutationSetRepeatedElementsSize() {
    List<Integer> list = newArrayList(1, 1, 1, 1, 2, 2, 3);
    Collection<List permutations =
        Collections2.orderedPermutations(list, Ordering.natural());

    assertPermutationsCount(105, permutations);
  }

  public void testOrderedPermutationSetSizeOverflow() {
    // 12 elements won't overflow
    assertEquals(479001600 /*12!*/, Collections2.orderedPermutations(
        newArrayList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)).size());
    // 13 elements overflow an int
    assertEquals(Integer.MAX_VALUE, Collections2.orderedPermutations(
        newArrayList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)).size());
    // 21 elements overflow a long
    assertEquals(Integer.MAX_VALUE, Collections2.orderedPermutations(
        newArrayList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
            16, 17, 18, 19, 20, 21)).size());

    // Almost force an overflow in the binomial coefficient calculation
    assertEquals(1391975640 /*C(34,14)*/, Collections2.orderedPermutations(
        concat(nCopies(20, 1), nCopies(14, 2))).size());
    // Do force an overflow in the binomial coefficient calculation
    assertEquals(Integer.MAX_VALUE, Collections2.orderedPermutations(
        concat(nCopies(21, 1), nCopies(14, 2))).size());
  }

  public void testOrderedPermutationSetContains() {
    List<Integer> list = newArrayList(3, 2, 1);
    Collection<List permutationSet =
        Collections2.orderedPermutations(list);

    assertTrue(permutationSet.contains(newArrayList(1, 2, 3)));
    assertTrue(permutationSet.contains(newArrayList(2, 3, 1)));
    assertFalse(permutationSet.contains(newArrayList(1, 2)));
    assertFalse(permutationSet.contains(newArrayList(1, 1, 2, 3)));
    assertFalse(permutationSet.contains(newArrayList(1, 2, 3, 4)));
    assertFalse(permutationSet.contains(null));
  }

  public void testPermutationSetEmpty() {
    Collection<List permutationSet =
        Collections2.permutations(Collections.<Integer>emptyList());

    assertEquals(1, permutationSet.size());
    assertTrue(permutationSet.contains(Collections.<Integer> emptyList()));

    Iterator<List permutations = permutationSet.iterator();
    assertNextPermutation(Collections.<Integer> emptyList(), permutations);
    assertNoMorePermutations(permutations);
  }

  public void testPermutationSetOneElement() {
    Iterator<List permutations =
        Collections2.permutations(Collections.<Integer> singletonList(1))
        .iterator();
    assertNextPermutation(newArrayList(1), permutations);
    assertNoMorePermutations(permutations);
  }

  public void testPermutationSetTwoElements() {
    Iterator<List permutations = Collections2.permutations(
        newArrayList(1, 2)).iterator();
    assertNextPermutation(newArrayList(1, 2), permutations);
    assertNextPermutation(newArrayList(2, 1), permutations);
    assertNoMorePermutations(permutations);
  }

  public void testPermutationSetThreeElements() {
    Iterator<List permutations = Collections2.permutations(
        newArrayList(1, 2, 3)).iterator();
    assertNextPermutation(newArrayList(1, 2, 3), permutations);
    assertNextPermutation(newArrayList(1, 3, 2), permutations);
    assertNextPermutation(newArrayList(3, 1, 2), permutations);

    assertNextPermutation(newArrayList(3, 2, 1), permutations);
    assertNextPermutation(newArrayList(2, 3, 1), permutations);
    assertNextPermutation(newArrayList(2, 1, 3), permutations);
    assertNoMorePermutations(permutations);
  }

  public void testPermutationSetThreeElementsOutOfOrder() {
    Iterator<List permutations = Collections2.permutations(
        newArrayList(3, 2, 1)).iterator();
    assertNextPermutation(newArrayList(3, 2, 1), permutations);
    assertNextPermutation(newArrayList(3, 1, 2), permutations);
    assertNextPermutation(newArrayList(1, 3, 2), permutations);

    assertNextPermutation(newArrayList(1, 2, 3), permutations);
    assertNextPermutation(newArrayList(2, 1, 3), permutations);
    assertNextPermutation(newArrayList(2, 3, 1), permutations);
    assertNoMorePermutations(permutations);
  }

  public void testPermutationSetThreeRepeatedElements() {
    Iterator<List permutations = Collections2.permutations(
        newArrayList(1, 1, 2)).iterator();
    assertNextPermutation(newArrayList(1, 1, 2), permutations);
    assertNextPermutation(newArrayList(1, 2, 1), permutations);
    assertNextPermutation(newArrayList(2, 1, 1), permutations);
    assertNextPermutation(newArrayList(2, 1, 1), permutations);
    assertNextPermutation(newArrayList(1, 2, 1), permutations);
    assertNextPermutation(newArrayList(1, 1, 2), permutations);
    assertNoMorePermutations(permutations);
  }

  public void testPermutationSetFourElements() {
    Iterator<List permutations = Collections2.permutations(
        newArrayList(1, 2, 3, 4)).iterator();
    assertNextPermutation(newArrayList(1, 2, 3, 4), permutations);
    assertNextPermutation(newArrayList(1, 2, 4, 3), permutations);
    assertNextPermutation(newArrayList(1, 4, 2, 3), permutations);
    assertNextPermutation(newArrayList(4, 1, 2, 3), permutations);

    assertNextPermutation(newArrayList(4, 1, 3, 2), permutations);
    assertNextPermutation(newArrayList(1, 4, 3, 2), permutations);
    assertNextPermutation(newArrayList(1, 3, 4, 2), permutations);
    assertNextPermutation(newArrayList(1, 3, 2, 4), permutations);

    assertNextPermutation(newArrayList(3, 1, 2, 4), permutations);
    assertNextPermutation(newArrayList(3, 1, 4, 2), permutations);
    assertNextPermutation(newArrayList(3, 4, 1, 2), permutations);
    assertNextPermutation(newArrayList(4, 3, 1, 2), permutations);

    assertNextPermutation(newArrayList(4, 3, 2, 1), permutations);
    assertNextPermutation(newArrayList(3, 4, 2, 1), permutations);
    assertNextPermutation(newArrayList(3, 2, 4, 1), permutations);
    assertNextPermutation(newArrayList(3, 2, 1, 4), permutations);

    assertNextPermutation(newArrayList(2, 3, 1, 4), permutations);
    assertNextPermutation(newArrayList(2, 3, 4, 1), permutations);
    assertNextPermutation(newArrayList(2, 4, 3, 1), permutations);
    assertNextPermutation(newArrayList(4, 2, 3, 1), permutations);

    assertNextPermutation(newArrayList(4, 2, 1, 3), permutations);
    assertNextPermutation(newArrayList(2, 4, 1, 3), permutations);
    assertNextPermutation(newArrayList(2, 1, 4, 3), permutations);
    assertNextPermutation(newArrayList(2, 1, 3, 4), permutations);
    assertNoMorePermutations(permutations);
  }

  public void testPermutationSetSize() {
    assertPermutationsCount(1,
        Collections2.permutations(Collections.<Integer>emptyList()));
    assertPermutationsCount(1, Collections2.permutations(newArrayList(1)));
    assertPermutationsCount(2, Collections2.permutations(newArrayList(1, 2)));
    assertPermutationsCount(6,
        Collections2.permutations(newArrayList(1, 2, 3)));
    assertPermutationsCount(5040,
        Collections2.permutations(newArrayList(1, 2, 3, 4, 5, 6, 7)));
    assertPermutationsCount(40320,
        Collections2.permutations(newArrayList(1, 2, 3, 4, 5, 6, 7, 8)));
  }

  public void testPermutationSetSizeOverflow() {
    // 13 elements overflow an int
    assertEquals(Integer.MAX_VALUE, Collections2.permutations(newArrayList(
        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)).size());
    // 21 elements overflow a long
    assertEquals(Integer.MAX_VALUE, Collections2.orderedPermutations(
        newArrayList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
            16, 17, 18, 19, 20)).size());
    assertEquals(Integer.MAX_VALUE, Collections2.orderedPermutations(
        newArrayList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
            16, 17, 18, 19, 20, 21)).size());
  }

  public void testPermutationSetContains() {
    List<Integer> list = newArrayList(3, 2, 1);
    Collection<List permutationSet =
        Collections2.permutations(list);

    assertTrue(permutationSet.contains(newArrayList(1, 2, 3)));
    assertTrue(permutationSet.contains(newArrayList(2, 3, 1)));
    assertFalse(permutationSet.contains(newArrayList(1, 2)));
    assertFalse(permutationSet.contains(newArrayList(1, 1, 2, 3)));
    assertFalse(permutationSet.contains(newArrayList(1, 2, 3, 4)));
    assertFalse(permutationSet.contains(null));
  }

  private <T> void assertNextPermutation(List expectedPermutation,
      Iterator<List permutations) {
    assertTrue("Expected another permutation, but there was none.",
        permutations.hasNext());
    assertEquals(expectedPermutation, permutations.next());
  }

  private <T> void assertNoMorePermutations(
      Iterator<List permutations) {
    assertFalse("Expected no more permutations, but there was one.",
        permutations.hasNext());
    try {
      permutations.next();
      fail("Expected NoSuchElementException.");
    } catch (NoSuchElementException expected) {}
  }

  private <T> void assertPermutationsCount(int expected,
      Collection<List permutationSet) {
    assertEquals(expected, permutationSet.size());
    Iterator<List permutations = permutationSet.iterator();
    for (int i = 0; i < expected; i++) {
      assertTrue(permutations.hasNext());
      permutations.next();
    }
    assertNoMorePermutations(permutations);
  }

  public void testToStringImplWithNullEntries() throws Exception {
    List<String> list = Lists.newArrayList();
    list.add("foo");
    list.add(null);

    assertEquals(list.toString(), Collections2.toStringImpl(list));
  }

}

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