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Java example source code file (Asserts.java)

This example Java source code file (Asserts.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

asserts, bytearrayinputstream, bytearrayoutputstream, expected, illegalargumentexception, interruptedexception, ioexception, object, referencequeue, runtimeexception, source, string, suppresswarnings, weakreference

The Asserts.java Java example source code

/**
 * Copyright (C) 2008 Google Inc.
 *
 * 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.inject;

import static com.google.inject.internal.InternalFlags.IncludeStackTraceOption;
import static com.google.inject.internal.InternalFlags.getIncludeStackTraceOption;
import static junit.framework.Assert.assertEquals;
import static junit.framework.Assert.assertNotNull;
import static junit.framework.Assert.assertSame;
import static junit.framework.Assert.assertTrue;

import com.google.common.base.Function;
import com.google.common.base.Joiner;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.common.testing.GcFinalization;

import junit.framework.Assert;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.NotSerializableException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;

/**
 * @author jessewilson@google.com (Jesse Wilson)
 */
public class Asserts {
  private Asserts() {}

  /**
   * Returns the String that would appear in an error message for this chain of classes 
   * as modules.
   */
  public static String asModuleChain(Class... classes) {
    return Joiner.on(" -> ").appendTo(new StringBuilder(" (via modules: "),
        Iterables.transform(ImmutableList.copyOf(classes), new Function<Class, String>() {
          @Override
          public String apply(Class input) {
            return input.getName();
          }
        })).append(")").toString();
  }

  /**
   * Returns the source file appears in error messages based on {@link 
   * #getIncludeStackTraceOption()} value.
   */
  public static String getDeclaringSourcePart(Class clazz) {
    if (getIncludeStackTraceOption() == IncludeStackTraceOption.OFF) {
      return ".configure(Unknown Source";
    }
    return ".configure(" + clazz.getSimpleName() + ".java:";
  }

  /**
   * Returns true if {@link #getIncludeStackTraceOption()} returns {@link
   * IncludeStackTraceOption#OFF}.
   */
  public static boolean isIncludeStackTraceOff() {
    return getIncludeStackTraceOption() == IncludeStackTraceOption.OFF;
  }

  /**
   * Returns true if {@link #getIncludeStackTraceOption()} returns {@link
   * IncludeStackTraceOption#COMPLETE}.
   */
  public static boolean isIncludeStackTraceComplete() {
    return getIncludeStackTraceOption() == IncludeStackTraceOption.COMPLETE;
  }

  /**
   * Fails unless {@code expected.equals(actual)}, {@code
   * actual.equals(expected)} and their hash codes are equal. This is useful
   * for testing the equals method itself.
   */
  public static void assertEqualsBothWays(Object expected, Object actual) {
    assertNotNull(expected);
    assertNotNull(actual);
    assertEquals("expected.equals(actual)", actual, expected);
    assertEquals("actual.equals(expected)", expected, actual);
    assertEquals("hashCode", expected.hashCode(), actual.hashCode());
  }

  /**
   * Fails unless {@code text} includes all {@code substrings}, in order.
   */
  public static void assertContains(String text, String... substrings) {
    /*if[NO_AOP]
    // when we strip out bytecode manipulation, we lose the ability to generate some source lines.
    if (text.contains("(Unknown Source)")) {
      return;
    }
    end[NO_AOP]*/

    int startingFrom = 0;
    for (String substring : substrings) {
      int index = text.indexOf(substring, startingFrom);
      assertTrue(String.format("Expected \"%s\" to contain substring \"%s\"", text, substring),
          index >= startingFrom);
      startingFrom = index + substring.length();
    }

    String lastSubstring = substrings[substrings.length - 1];
    assertTrue(String.format("Expected \"%s\" to contain substring \"%s\" only once),",
        text, lastSubstring), text.indexOf(lastSubstring, startingFrom) == -1);
  }

  /**
   * Fails unless {@code object} doesn't equal itself when reserialized.
   */
  public static void assertEqualWhenReserialized(Object object)
      throws IOException {
    Object reserialized = reserialize(object);
    assertEquals(object, reserialized);
    assertEquals(object.hashCode(), reserialized.hashCode());
  }

  /**
   * Fails unless {@code object} has the same toString value when reserialized.
   */
  public static void assertSimilarWhenReserialized(Object object) throws IOException {
    Object reserialized = reserialize(object);
    assertEquals(object.toString(), reserialized.toString());
  }

  public static <E> E reserialize(E original) throws IOException {
    try {
      ByteArrayOutputStream out = new ByteArrayOutputStream();
      new ObjectOutputStream(out).writeObject(original);
      ByteArrayInputStream in = new ByteArrayInputStream(out.toByteArray());
      @SuppressWarnings("unchecked") // the reserialized type is assignable
      E reserialized = (E) new ObjectInputStream(in).readObject();
      return reserialized;
    } catch (ClassNotFoundException e) {
      throw new RuntimeException(e);
    }
  }

  public static void assertNotSerializable(Object object) throws IOException {
    try {
      reserialize(object);
      Assert.fail();
    } catch (NotSerializableException expected) {
    }
  }

  public static void awaitFullGc() {
    // GcFinalization *should* do it, but doesn't work well in practice...
    // so we put a second latch and wait for a ReferenceQueue to tell us.
    ReferenceQueue<Object> queue = new ReferenceQueue();
    WeakReference ref = new WeakReference<Object>(new Object(), queue);
    GcFinalization.awaitFullGc();
    try {
      assertSame("queue didn't return ref in time", ref, queue.remove(5000));
    } catch (IllegalArgumentException e) {
      throw new RuntimeException(e);
    } catch (InterruptedException e) {
      throw new RuntimeException(e);
    }
  }

  public static void awaitClear(WeakReference<?> ref) {
    // GcFinalization *should* do it, but doesn't work well in practice...
    // so we put a second latch and wait for a ReferenceQueue to tell us.
    Object data = ref.get();
    ReferenceQueue<Object> queue = null;
    WeakReference extraRef = null;
    if (data != null) {
      queue = new ReferenceQueue<Object>();
      extraRef = new WeakReference<Object>(data, queue);
      data = null;
    }
    GcFinalization.awaitClear(ref);
    if (queue != null) {
      try {
        assertSame("queue didn't return ref in time", extraRef, queue.remove(5000));
      } catch (IllegalArgumentException e) {
        throw new RuntimeException(e);
      } catch (InterruptedException e) {
        throw new RuntimeException(e);
      }
    }
  }
}

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