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Java example source code file (TypesTest.java)

This example Java source code file (TypesTest.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

charsequence, genericarraytype, illegalargumentexception, inner, list, nosuchfieldexception, outer, owning, parameterizedtype, primitive, reflection, set, suppresswarnings, typeliteral, util, wildcardtype

The TypesTest.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.util;

import static com.google.inject.Asserts.assertContains;
import static com.google.inject.Asserts.assertEqualWhenReserialized;
import static com.google.inject.Asserts.assertEqualsBothWays;
import static com.google.inject.util.Types.subtypeOf;
import static com.google.inject.util.Types.supertypeOf;

import com.google.inject.TypeLiteral;
import com.google.inject.internal.MoreTypes;

import junit.framework.Assert;
import junit.framework.TestCase;

import java.io.IOException;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.WildcardType;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * @author jessewilson@google.com (Jesse Wilson)
 */
public class TypesTest extends TestCase {

  // generic types for comparison
  Map<String, Integer> a;
  Inner<Float, Double> b;
  List<Set c;
  List<String> d;
  Set<String> e;
  Outer<String>.Inner f;

  private ParameterizedType mapStringInteger;
  private ParameterizedType innerFloatDouble;
  private ParameterizedType listSetStringArray;
  private ParameterizedType listString;
  private ParameterizedType setString;
  private ParameterizedType outerInner;
  private GenericArrayType setStringArray;

  @Override
  protected void setUp() throws Exception {
    super.setUp();
    mapStringInteger = (ParameterizedType) getClass().getDeclaredField("a").getGenericType();
    innerFloatDouble = (ParameterizedType) getClass().getDeclaredField("b").getGenericType();
    listSetStringArray = (ParameterizedType) getClass().getDeclaredField("c").getGenericType();
    listString = (ParameterizedType) getClass().getDeclaredField("d").getGenericType();
    setString = (ParameterizedType) getClass().getDeclaredField("e").getGenericType();
    outerInner = (ParameterizedType) getClass().getDeclaredField("f").getGenericType();
    setStringArray = (GenericArrayType) listSetStringArray.getActualTypeArguments()[0];
  }

  public void testListSetMap() {
    assertEqualsBothWays(mapStringInteger, Types.mapOf(String.class, Integer.class));
    assertEqualsBothWays(listString, Types.listOf(String.class));
    assertEqualsBothWays(setString, Types.setOf(String.class));
  }

  public void testDefensiveCopies() {
    Type[] arguments = new Type[] { String.class, Integer.class };
    ParameterizedType parameterizedType = Types.newParameterizedType(Map.class, arguments);
    arguments[0] = null;
    assertEquals(String.class, parameterizedType.getActualTypeArguments()[0]);
    parameterizedType.getActualTypeArguments()[1] = null;
    assertEquals(Integer.class, parameterizedType.getActualTypeArguments()[1]);
  }

  public void testTypeWithOwnerType() {
    ParameterizedType actual = Types.newParameterizedTypeWithOwner(
        TypesTest.class, Inner.class, Float.class, Double.class);
    assertEquals(TypesTest.class, actual.getOwnerType());
    assertEqualsBothWays(innerFloatDouble, actual);
    // The JDK prints this out as:
    //     com.google.inject.util.TypesTest.com.google.inject.util.TypesTest$Inner<java.lang.Float, java.lang.Double>
    // and we think that's wrong, so the assertEquals comparison is worthless. :-(
//    assertEquals(innerFloatDouble.toString(), actual.toString());
    
    // We think the correct comparison is:
    assertEquals("com.google.inject.util.TypesTest$Inner<java.lang.Float, java.lang.Double>", actual.toString());
  }

  public void testTypeParametersMustNotBePrimitives() {
    try {
      Types.newParameterizedType(Map.class, String.class, int.class);
      fail();
    } catch (IllegalArgumentException expected) {
      assertContains(expected.getMessage(),
          "Primitive types are not allowed in type parameters: int");
    }
  }

  public List<? extends CharSequence> wildcardExtends;
  public List<? super CharSequence> wildcardSuper;
  public List<?> wildcardObject;

  public void testWildcardTypes() throws NoSuchFieldException, IOException {
    assertEqualsBothWays(getWildcard("wildcardSuper"), supertypeOf(CharSequence.class));
    assertEqualsBothWays(getWildcard("wildcardExtends"), subtypeOf(CharSequence.class));
    assertEqualsBothWays(getWildcard("wildcardObject"), subtypeOf(Object.class));

    assertEquals("? super java.lang.CharSequence", supertypeOf(CharSequence.class).toString());
    assertEquals("? extends java.lang.CharSequence", subtypeOf(CharSequence.class).toString());
    assertEquals("?", subtypeOf(Object.class).toString());

    assertEqualWhenReserialized(supertypeOf(CharSequence.class));
    assertEqualWhenReserialized(subtypeOf(CharSequence.class));
  }
  
  public void testWildcardBoundsMustNotBePrimitives() {
    try {
      supertypeOf(int.class);
      fail();
    } catch (IllegalArgumentException expected) {
      assertContains(expected.getMessage(),
          "Primitive types are not allowed in wildcard bounds: int");
    }

    try {
      subtypeOf(int.class);
      fail();
    } catch (IllegalArgumentException expected) {
      assertContains(expected.getMessage(),
          "Primitive types are not allowed in wildcard bounds: int");
    }
  }

  private WildcardType getWildcard(String fieldName) throws NoSuchFieldException {
    ParameterizedType type = (ParameterizedType) getClass().getField(fieldName).getGenericType();
    return (WildcardType) type.getActualTypeArguments()[0];
  }

  public void testEqualsAndHashcode() {
    ParameterizedType parameterizedType
        = Types.newParameterizedType(Map.class, String.class, Integer.class);
    assertEqualsBothWays(mapStringInteger, parameterizedType);
    assertEquals(mapStringInteger.toString(), parameterizedType.toString());

    GenericArrayType genericArrayType = Types.arrayOf(Types.arrayOf(
        Types.newParameterizedType(Set.class, String.class)));
    assertEqualsBothWays(setStringArray, genericArrayType);
    assertEquals(setStringArray.toString(), genericArrayType.toString());
  }

  public void testToString() {
    Assert.assertEquals("java.lang.String", MoreTypes.typeToString(String.class));
    assertEquals("java.util.Set<java.lang.String>[][]", MoreTypes.typeToString(setStringArray));
    assertEquals("java.util.Map<java.lang.String, java.lang.Integer>",
        MoreTypes.typeToString(mapStringInteger));
    assertEquals("java.util.List<java.util.Set",
        MoreTypes.typeToString(listSetStringArray));
    assertEquals(innerFloatDouble.toString(),
        MoreTypes.typeToString(innerFloatDouble));
  }

  static class Owning<A> {}

  /**
   * Ensure that owning types are required when necessary, and forbidden
   * otherwise.
   */
  public void testCanonicalizeRequiresOwnerTypes() {
    try {
      Types.newParameterizedType(Owning.class, String.class);
      fail();
    } catch (IllegalArgumentException expected) {
      assertContains(expected.getMessage(),
          "No owner type for enclosed " + Owning.class);
    }

    try {
      Types.newParameterizedTypeWithOwner(Object.class, Set.class, String.class);
    } catch (IllegalArgumentException expected) {
      assertContains(expected.getMessage(),
          "Owner type for unenclosed " + Set.class);
    }
  }

  @SuppressWarnings("UnusedDeclaration")
  class Inner<T1, T2> {}
  
  public void testInnerParameterizedEvenWithZeroArgs() {
    TypeLiteral<Outer type = new TypeLiteral.Inner>() {};
    assertEqualsBothWays(outerInner, type.getType());

    ParameterizedType parameterizedType = (ParameterizedType) type.getType();
    assertEquals(0, parameterizedType.getActualTypeArguments().length);
    assertEquals(new TypeLiteral<Outer() {}.getType(), parameterizedType.getOwnerType());
    assertEquals(Outer.Inner.class, parameterizedType.getRawType());
  }

  static class Outer<T> {
    class Inner {}
  }
}

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