common/src/test/core/org/apache/hadoop/util/TestGenericsUtil.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.hadoop.util;

import java.util.ArrayList;
import java.util.List;

import junit.framework.TestCase;

import org.apache.hadoop.conf.Configuration;

public class TestGenericsUtil extends TestCase {

  public void testToArray() {
    
    //test a list of size 10
    List<Integer> list = new ArrayList<Integer>(); 
    
    for(int i=0; i<10; i++) {
      list.add(i);
    }
    
    Integer[] arr = GenericsUtil.toArray(list);
    
    for (int i = 0; i < arr.length; i++) {
      assertEquals(list.get(i), arr[i]);
    }
  }
  
  public void testWithEmptyList() {
    try {
      List<String> list = new ArrayList<String>();
      String[] arr = GenericsUtil.toArray(list);
      fail("Empty array should throw exception");
      System.out.println(arr); //use arr so that compiler will not complain
      
    }catch (IndexOutOfBoundsException ex) {
      //test case is successful
    }
  }
 
  public void testWithEmptyList2() {
    List<String> list = new ArrayList<String>();
    //this method should not throw IndexOutOfBoundsException
    String[] arr = GenericsUtil.<String>toArray(String.class, list);
    
    assertEquals(0, arr.length);
  }
  
  /** This class uses generics */
  private class GenericClass<T> {
    T dummy;
    List<T> list = new ArrayList<T>();
    
    void add(T item) {
      list.add(item);
    }
    
    T[] funcThatUsesToArray() {
      T[] arr = GenericsUtil.toArray(list);
      return arr;
    }
  }
  
  public void testWithGenericClass() {
    
    GenericClass<String> testSubject = new GenericClass<String>();
    
    testSubject.add("test1");
    testSubject.add("test2");
    
    try {
      //this cast would fail, if we had not used GenericsUtil.toArray, since the 
      //rmethod would return Object[] rather than String[]
      String[] arr = testSubject.funcThatUsesToArray();
      
      assertEquals("test1", arr[0]);
      assertEquals("test2", arr[1]);
      
    }catch (ClassCastException ex) {
      fail("GenericsUtil#toArray() is not working for generic classes");
    }
    
  }
  
  public void testGenericOptionsParser() throws Exception {
     GenericOptionsParser parser = new GenericOptionsParser(
        new Configuration(), new String[] {"-jt"});
    assertEquals(parser.getRemainingArgs().length, 0);
    
    //  test if -D accepts -Dx=y=z
    parser = 
      new GenericOptionsParser(new Configuration(), 
                               new String[] {"-Dx=y=z"});
    assertEquals(parser.getConfiguration().get("x"), "y=z");
  }
  
  public void testGetClass() {
    
    //test with Integer
    Integer x = new Integer(42); 
    Class<Integer> c = GenericsUtil.getClass(x);
    assertEquals(Integer.class, c);
    
    //test with GenericClass<Integer>
    GenericClass<Integer> testSubject = new GenericClass<Integer>();
    Class<GenericClass<Integer>> c2 = GenericsUtil.getClass(testSubject);
    assertEquals(GenericClass.class, c2);
  }
  
}