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Java example source code file (FunctionsTest.java)

This example Java source code file (FunctionsTest.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

countingsupplier, equalstester, function, gwtincompatible, illegalargumentexception, integer, map, one, override, serializabletester, string, three, two, util

The FunctionsTest.java Java example source code

/*
 * Copyright (C) 2005 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.base;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Maps;
import com.google.common.testing.ClassSanityTester;
import com.google.common.testing.EqualsTester;
import com.google.common.testing.NullPointerTester;
import com.google.common.testing.SerializableTester;

import junit.framework.TestCase;

import java.io.Serializable;
import java.util.Map;

/**
 * Tests for {@link Functions}.
 *
 * @author Mike Bostock
 * @author Vlad Patryshev
 */
@GwtCompatible(emulated = true)
public class FunctionsTest extends TestCase {

  public void testIdentity_same() {
    Function<String, String> identity = Functions.identity();
    assertNull(identity.apply(null));
    assertSame("foo", identity.apply("foo"));
  }

  public void testIdentity_notSame() {
    Function<Long, Long> identity = Functions.identity();
    assertNotSame(new Long(135135L), identity.apply(new Long(135135L)));
  }

  @GwtIncompatible // SerializableTester
  public void testIdentitySerializable() {
    checkCanReserializeSingleton(Functions.identity());
  }

  public void testToStringFunction_apply() {
    assertEquals("3", Functions.toStringFunction().apply(3));
    assertEquals("hiya", Functions.toStringFunction().apply("hiya"));
    assertEquals("I'm a string",
        Functions.toStringFunction().apply(
            new Object() {
              @Override public String toString() {
                return "I'm a string";
              }
            }));
    try {
      Functions.toStringFunction().apply(null);
      fail("expected NullPointerException");
    } catch (NullPointerException e) {
      // expected
    }
  }

  @GwtIncompatible // SerializableTester
  public void testToStringFunctionSerializable() {
    checkCanReserializeSingleton(Functions.toStringFunction());
  }

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

  public void testForMapWithoutDefault() {
    Map<String, Integer> map = Maps.newHashMap();
    map.put("One", 1);
    map.put("Three", 3);
    map.put("Null", null);
    Function<String, Integer> function = Functions.forMap(map);

    assertEquals(1, function.apply("One").intValue());
    assertEquals(3, function.apply("Three").intValue());
    assertNull(function.apply("Null"));

    try {
      function.apply("Two");
      fail();
    } catch (IllegalArgumentException expected) {
    }

    new EqualsTester()
        .addEqualityGroup(function, Functions.forMap(map))
        .addEqualityGroup(Functions.forMap(map, 42))
        .testEquals();
  }

  @GwtIncompatible // SerializableTester
  public void testForMapWithoutDefaultSerializable() {
    checkCanReserialize(Functions.forMap(ImmutableMap.of(1, 2)));
  }

  public void testForMapWithDefault() {
    Map<String, Integer> map = Maps.newHashMap();
    map.put("One", 1);
    map.put("Three", 3);
    map.put("Null", null);
    Function<String, Integer> function = Functions.forMap(map, 42);

    assertEquals(1, function.apply("One").intValue());
    assertEquals(42, function.apply("Two").intValue());
    assertEquals(3, function.apply("Three").intValue());
    assertNull(function.apply("Null"));

    new EqualsTester()
        .addEqualityGroup(function, Functions.forMap(map, 42))
        .addEqualityGroup(Functions.forMap(map))
        .addEqualityGroup(Functions.forMap(map, null))
        .addEqualityGroup(Functions.forMap(map, 43))
        .testEquals();
  }

  @GwtIncompatible // SerializableTester
  public void testForMapWithDefault_includeSerializable() {
    Map<String, Integer> map = Maps.newHashMap();
    map.put("One", 1);
    map.put("Three", 3);
    Function<String, Integer> function = Functions.forMap(map, 42);

    assertEquals(1, function.apply("One").intValue());
    assertEquals(42, function.apply("Two").intValue());
    assertEquals(3, function.apply("Three").intValue());

    new EqualsTester()
        .addEqualityGroup(
            function,
            Functions.forMap(map, 42),
            SerializableTester.reserialize(function))
        .addEqualityGroup(Functions.forMap(map))
        .addEqualityGroup(Functions.forMap(map, null))
        .addEqualityGroup(Functions.forMap(map, 43))
        .testEquals();
  }

  @GwtIncompatible // SerializableTester
  public void testForMapWithDefaultSerializable() {
    checkCanReserialize(Functions.forMap(ImmutableMap.of(1, 2), 3));
  }

  public void testForMapWithDefault_null() {
    ImmutableMap<String, Integer> map = ImmutableMap.of("One", 1);
    Function<String, Integer> function = Functions.forMap(map, null);

    assertEquals((Integer) 1, function.apply("One"));
    assertNull(function.apply("Two"));

    // check basic sanity of equals and hashCode
    new EqualsTester()
        .addEqualityGroup(function)
        .addEqualityGroup(Functions.forMap(map, 1))
        .testEquals();
  }

  @GwtIncompatible // SerializableTester
  public void testForMapWithDefault_null_compareWithSerializable() {
    ImmutableMap<String, Integer> map = ImmutableMap.of("One", 1);
    Function<String, Integer> function = Functions.forMap(map, null);

    assertEquals((Integer) 1, function.apply("One"));
    assertNull(function.apply("Two"));

    // check basic sanity of equals and hashCode
    new EqualsTester()
        .addEqualityGroup(function, SerializableTester.reserialize(function))
        .addEqualityGroup(Functions.forMap(map, 1))
        .testEquals();
  }

  public void testForMapWildCardWithDefault() {
    Map<String, Integer> map = Maps.newHashMap();
    map.put("One", 1);
    map.put("Three", 3);
    Number number = Double.valueOf(42);
    Function<String, Number> function = Functions.forMap(map, number);

    assertEquals(1, function.apply("One").intValue());
    assertEquals(number, function.apply("Two"));
    assertEquals(3L, function.apply("Three").longValue());
  }

  public void testComposition() {
    Map<String, Integer> mJapaneseToInteger = Maps.newHashMap();
    mJapaneseToInteger.put("Ichi", 1);
    mJapaneseToInteger.put("Ni", 2);
    mJapaneseToInteger.put("San", 3);
    Function<String, Integer> japaneseToInteger =
        Functions.forMap(mJapaneseToInteger);

    Map<Integer, String> mIntegerToSpanish = Maps.newHashMap();
    mIntegerToSpanish.put(1, "Uno");
    mIntegerToSpanish.put(3, "Tres");
    mIntegerToSpanish.put(4, "Cuatro");
    Function<Integer, String> integerToSpanish =
        Functions.forMap(mIntegerToSpanish);

    Function<String, String> japaneseToSpanish =
        Functions.compose(integerToSpanish, japaneseToInteger);

    assertEquals("Uno", japaneseToSpanish.apply("Ichi"));
    try {
      japaneseToSpanish.apply("Ni");
      fail();
    } catch (IllegalArgumentException e) {
    }
    assertEquals("Tres", japaneseToSpanish.apply("San"));
    try {
      japaneseToSpanish.apply("Shi");
      fail();
    } catch (IllegalArgumentException e) {
    }

    new EqualsTester()
        .addEqualityGroup(
            japaneseToSpanish,
            Functions.compose(integerToSpanish, japaneseToInteger))
        .addEqualityGroup(japaneseToInteger)
        .addEqualityGroup(integerToSpanish)
        .addEqualityGroup(
            Functions.compose(japaneseToInteger, integerToSpanish))
        .testEquals();
  }

  @GwtIncompatible // SerializableTester
  public void testComposition_includeReserializabled() {
    Map<String, Integer> mJapaneseToInteger = Maps.newHashMap();
    mJapaneseToInteger.put("Ichi", 1);
    mJapaneseToInteger.put("Ni", 2);
    mJapaneseToInteger.put("San", 3);
    Function<String, Integer> japaneseToInteger =
        Functions.forMap(mJapaneseToInteger);

    Map<Integer, String> mIntegerToSpanish = Maps.newHashMap();
    mIntegerToSpanish.put(1, "Uno");
    mIntegerToSpanish.put(3, "Tres");
    mIntegerToSpanish.put(4, "Cuatro");
    Function<Integer, String> integerToSpanish =
        Functions.forMap(mIntegerToSpanish);

    Function<String, String> japaneseToSpanish =
        Functions.compose(integerToSpanish, japaneseToInteger);

    new EqualsTester()
        .addEqualityGroup(
            japaneseToSpanish,
            Functions.compose(integerToSpanish, japaneseToInteger),
            SerializableTester.reserialize(japaneseToSpanish))
        .addEqualityGroup(japaneseToInteger)
        .addEqualityGroup(integerToSpanish)
        .addEqualityGroup(
            Functions.compose(japaneseToInteger, integerToSpanish))
        .testEquals();
  }

  public void testCompositionWildcard() {
    Map<String, Integer> mapJapaneseToInteger = Maps.newHashMap();
    Function<String, Integer> japaneseToInteger =
        Functions.forMap(mapJapaneseToInteger);

    Function<Object, String> numberToSpanish = Functions.constant("Yo no se");

    Function<String, String> japaneseToSpanish =
        Functions.compose(numberToSpanish, japaneseToInteger);
  }

  private static class HashCodeFunction implements Function<Object, Integer> {
    @Override
    public Integer apply(Object o) {
      return (o == null) ? 0 : o.hashCode();
    }
  }

  public void testComposeOfFunctionsIsAssociative() {
    Map<Float, String> m = ImmutableMap.of(
        4.0f, "A", 3.0f, "B", 2.0f, "C", 1.0f, "D");
    Function<? super Integer, Boolean> h = Functions.constant(Boolean.TRUE);
    Function<? super String, Integer> g = new HashCodeFunction();
    Function<Float, String> f = Functions.forMap(m, "F");

    Function<Float, Boolean> c1 = Functions.compose(Functions.compose(h, g), f);
    Function<Float, Boolean> c2 = Functions.compose(h, Functions.compose(g, f));

    // Might be nice (eventually) to have:
    //     assertEquals(c1, c2);

    // But for now, settle for this:
    assertEquals(c1.hashCode(), c2.hashCode());

    assertEquals(c1.apply(1.0f), c2.apply(1.0f));
    assertEquals(c1.apply(5.0f), c2.apply(5.0f));
  }

  public void testComposeOfPredicateAndFunctionIsAssociative() {
    Map<Float, String> m = ImmutableMap.of(
        4.0f, "A", 3.0f, "B", 2.0f, "C", 1.0f, "D");
    Predicate<? super Integer> h = Predicates.equalTo(42);
    Function<? super String, Integer> g = new HashCodeFunction();
    Function<Float, String> f = Functions.forMap(m, "F");

    Predicate<Float> p1 = Predicates.compose(Predicates.compose(h, g), f);
    Predicate<Float> p2 = Predicates.compose(h, Functions.compose(g, f));

    // Might be nice (eventually) to have:
    //     assertEquals(p1, p2);

    // But for now, settle for this:
    assertEquals(p1.hashCode(), p2.hashCode());

    assertEquals(p1.apply(1.0f), p2.apply(1.0f));
    assertEquals(p1.apply(5.0f), p2.apply(5.0f));
  }

  public void testForPredicate() {
    Function<Object, Boolean> alwaysTrue =
        Functions.forPredicate(Predicates.alwaysTrue());
    Function<Object, Boolean> alwaysFalse =
        Functions.forPredicate(Predicates.alwaysFalse());

    assertTrue(alwaysTrue.apply(0));
    assertFalse(alwaysFalse.apply(0));

    new EqualsTester()
        .addEqualityGroup(
            alwaysTrue, Functions.forPredicate(Predicates.alwaysTrue()))
        .addEqualityGroup(alwaysFalse)
        .addEqualityGroup(Functions.identity())
        .testEquals();
  }

  @GwtIncompatible // SerializableTester
  public void testForPredicateSerializable() {
    checkCanReserialize(Functions.forPredicate(Predicates.equalTo(5)));
  }

  public void testConstant() {
    Function<Object, Object> f = Functions.constant("correct");
    assertEquals("correct", f.apply(new Object()));
    assertEquals("correct", f.apply(null));

    Function<Object, String> g = Functions.constant(null);
    assertEquals(null, g.apply(2));
    assertEquals(null, g.apply(null));

    new EqualsTester()
        .addEqualityGroup(f, Functions.constant("correct"))
        .addEqualityGroup(Functions.constant("incorrect"))
        .addEqualityGroup(Functions.toStringFunction())
        .addEqualityGroup(g)
        .testEquals();

    new EqualsTester()
        .addEqualityGroup(g, Functions.constant(null))
        .addEqualityGroup(Functions.constant("incorrect"))
        .addEqualityGroup(Functions.toStringFunction())
        .addEqualityGroup(f)
        .testEquals();
  }

  @GwtIncompatible // SerializableTester
  public void testConstantSerializable() {
    checkCanReserialize(Functions.constant(5));
  }

  private static class CountingSupplier
      implements Supplier<Integer>, Serializable {

    private static final long serialVersionUID = 0;

    private int value;

    @Override
    public Integer get() {
      return ++value;
    }

    @Override
    public boolean equals(Object obj) {
      if (obj instanceof CountingSupplier) {
        return this.value == ((CountingSupplier) obj).value;
      }
      return false;
    }

    @Override
    public int hashCode() {
      return value;
    }
  }

  public void testForSupplier() {
    Supplier<Integer> supplier = new CountingSupplier();
    Function<Object, Integer> function = Functions.forSupplier(supplier);

    assertEquals(1, (int) function.apply(null));
    assertEquals(2, (int) function.apply("foo"));

    new EqualsTester()
        .addEqualityGroup(function, Functions.forSupplier(supplier))
        .addEqualityGroup(Functions.forSupplier(new CountingSupplier()))
        .addEqualityGroup(Functions.forSupplier(Suppliers.ofInstance(12)))
        .addEqualityGroup(Functions.toStringFunction())
        .testEquals();
  }

  @GwtIncompatible // SerializableTester
  public void testForSupplierSerializable() {
    checkCanReserialize(Functions.forSupplier(new CountingSupplier()));
  }

  @GwtIncompatible // reflection
  public void testNulls() throws Exception {
    new ClassSanityTester().forAllPublicStaticMethods(Functions.class).testNulls();
  }

  @GwtIncompatible // reflection
  @AndroidIncompatible // TODO(cpovirk): ClassNotFoundException: com.google.common.base.Function
  // (I suspect that this and the other similar failures happen with ArbitraryInstances proxies.)
  public void testEqualsAndSerializable() throws Exception {
    new ClassSanityTester().forAllPublicStaticMethods(Functions.class).testEqualsAndSerializable();
  }

  @GwtIncompatible // SerializableTester
  private static <Y> void checkCanReserialize(Function f) {
    Function<? super Integer, Y> g = SerializableTester.reserializeAndAssert(f);
    for (int i = 1; i < 5; i++) {
      // convoluted way to check that the same result happens from each
      Y expected = null;
      try {
        expected = f.apply(i);
      } catch (IllegalArgumentException e) {
        try {
          g.apply(i);
          fail();
        } catch (IllegalArgumentException ok) {
          continue;
        }
      }
      assertEquals(expected, g.apply(i));
    }
  }

  @GwtIncompatible // SerializableTester
  private static <Y> void checkCanReserializeSingleton(Function f) {
    Function<? super String, Y> g = SerializableTester.reserializeAndAssert(f);
    assertSame(f, g);
    for (Integer i = 1; i < 5; i++) {
      assertEquals(f.apply(i.toString()), g.apply(i.toString()));
    }
  }

}




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