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Java example source code file (EnumsTest.java)

This example Java source code file (EnumsTest.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

annotation, cheeto, converter, exampleannotation, exception, field, foo, gwtincompatible, honda, net, network, nullpointertester, optional, poodle, reflection, testenum, urlclassloader, util, weakreference

The EnumsTest.java Java example source code

/*
 * Copyright (C) 2011 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 static com.google.common.truth.Truth.assertThat;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.collect.ImmutableSet;
import com.google.common.testing.GcFinalization;
import com.google.common.testing.NullPointerTester;
import com.google.common.testing.SerializableTester;

import junit.framework.TestCase;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.ref.WeakReference;
import java.lang.reflect.Field;
import java.net.URLClassLoader;
import java.util.HashSet;
import java.util.Set;

/**
 * Tests for {@link Enums}.
 *
 * @author Steve McKay
 */
@GwtCompatible(emulated = true)
public class EnumsTest extends TestCase {

  private enum TestEnum {
    CHEETO,
    HONDA,
    POODLE,
  }

  private enum OtherEnum {}

  public void testGetIfPresent() {
    assertThat(Enums.getIfPresent(TestEnum.class, "CHEETO")).hasValue(TestEnum.CHEETO);
    assertThat(Enums.getIfPresent(TestEnum.class, "HONDA")).hasValue(TestEnum.HONDA);
    assertThat(Enums.getIfPresent(TestEnum.class, "POODLE")).hasValue(TestEnum.POODLE);

    assertThat(Enums.getIfPresent(TestEnum.class, "CHEETO")).isPresent();
    assertThat(Enums.getIfPresent(TestEnum.class, "HONDA")).isPresent();
    assertThat(Enums.getIfPresent(TestEnum.class, "POODLE")).isPresent();

    assertThat(Enums.getIfPresent(TestEnum.class, "CHEETO")).hasValue(TestEnum.CHEETO);
    assertThat(Enums.getIfPresent(TestEnum.class, "HONDA")).hasValue(TestEnum.HONDA);
    assertThat(Enums.getIfPresent(TestEnum.class, "POODLE")).hasValue(TestEnum.POODLE);
  }

  public void testGetIfPresent_caseSensitive() {
    assertThat(Enums.getIfPresent(TestEnum.class, "cHEETO")).isAbsent();
    assertThat(Enums.getIfPresent(TestEnum.class, "Honda")).isAbsent();
    assertThat(Enums.getIfPresent(TestEnum.class, "poodlE")).isAbsent();
  }

  public void testGetIfPresent_whenNoMatchingConstant() {
    assertThat(Enums.getIfPresent(TestEnum.class, "WOMBAT")).isAbsent();
  }

  @GwtIncompatible // weak references
  public void testGetIfPresent_doesNotPreventClassUnloading() throws Exception {
    WeakReference<?> shadowLoaderReference = doTestClassUnloading();
    GcFinalization.awaitClear(shadowLoaderReference);
  }

  // Create a second ClassLoader and use it to get a second version of the TestEnum class.
  // Run Enums.getIfPresent on that other TestEnum and then return a WeakReference containing the
  // new ClassLoader. If Enums.getIfPresent does caching that prevents the shadow TestEnum
  // (and therefore its ClassLoader) from being unloaded, then this WeakReference will never be
  // cleared.
  @GwtIncompatible // weak references
  private WeakReference<?> doTestClassUnloading() throws Exception {
    URLClassLoader myLoader = (URLClassLoader) getClass().getClassLoader();
    URLClassLoader shadowLoader = new URLClassLoader(myLoader.getURLs(), null);
    @SuppressWarnings("unchecked")
    Class<TestEnum> shadowTestEnum =
        (Class<TestEnum>) Class.forName(TestEnum.class.getName(), false, shadowLoader);
    assertNotSame(shadowTestEnum, TestEnum.class);
    // We can't write Set<TestEnum> because that is a Set of the TestEnum from the original
    // ClassLoader.
    Set<Object> shadowConstants = new HashSet();
    for (TestEnum constant : TestEnum.values()) {
      Optional<TestEnum> result = Enums.getIfPresent(shadowTestEnum, constant.name());
      assertThat(result).isPresent();
      shadowConstants.add(result.get());
    }
    assertEquals(ImmutableSet.<Object>copyOf(shadowTestEnum.getEnumConstants()), shadowConstants);
    Optional<TestEnum> result = Enums.getIfPresent(shadowTestEnum, "blibby");
    assertThat(result).isAbsent();
    return new WeakReference<ClassLoader>(shadowLoader);
  }

  public void testStringConverter_convert() {
    Converter<String, TestEnum> converter = Enums.stringConverter(TestEnum.class);
    assertEquals(TestEnum.CHEETO, converter.convert("CHEETO"));
    assertEquals(TestEnum.HONDA, converter.convert("HONDA"));
    assertEquals(TestEnum.POODLE, converter.convert("POODLE"));
    assertNull(converter.convert(null));
    assertNull(converter.reverse().convert(null));
  }

  public void testStringConverter_convertError() {
    Converter<String, TestEnum> converter = Enums.stringConverter(TestEnum.class);
    try {
      converter.convert("xxx");
      fail();
    } catch (IllegalArgumentException expected) {
    }
  }

  public void testStringConverter_reverse() {
    Converter<String, TestEnum> converter = Enums.stringConverter(TestEnum.class);
    assertEquals("CHEETO", converter.reverse().convert(TestEnum.CHEETO));
    assertEquals("HONDA", converter.reverse().convert(TestEnum.HONDA));
    assertEquals("POODLE", converter.reverse().convert(TestEnum.POODLE));
  }

  @GwtIncompatible // NullPointerTester
  public void testStringConverter_nullPointerTester() throws Exception {
    Converter<String, TestEnum> converter = Enums.stringConverter(TestEnum.class);
    NullPointerTester tester = new NullPointerTester();
    tester.testAllPublicInstanceMethods(converter);
  }

  public void testStringConverter_nullConversions() {
    Converter<String, TestEnum> converter = Enums.stringConverter(TestEnum.class);
    assertNull(converter.convert(null));
    assertNull(converter.reverse().convert(null));
  }

  @GwtIncompatible // Class.getName()
  public void testStringConverter_toString() {
    assertEquals(
        "Enums.stringConverter(com.google.common.base.EnumsTest$TestEnum.class)",
        Enums.stringConverter(TestEnum.class).toString());
  }

  public void testStringConverter_serialization() {
    SerializableTester.reserializeAndAssert(Enums.stringConverter(TestEnum.class));
  }

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

  @Retention(RetentionPolicy.RUNTIME)
  private @interface ExampleAnnotation {}

  private enum AnEnum {
    @ExampleAnnotation FOO,
    BAR
  }

  @GwtIncompatible // reflection
  public void testGetField() {
    Field foo = Enums.getField(AnEnum.FOO);
    assertEquals("FOO", foo.getName());
    assertTrue(foo.isAnnotationPresent(ExampleAnnotation.class));

    Field bar = Enums.getField(AnEnum.BAR);
    assertEquals("BAR", bar.getName());
    assertFalse(bar.isAnnotationPresent(ExampleAnnotation.class));
  }
}

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