Java example source code file (EnumsTest.java)

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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