MapInitializationTest.java

package com.objectpartners.buesing.util;

import com.google.common.collect.ImmutableMap;
import org.junit.Assert;
import org.junit.Test;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

import static com.objectpartners.buesing.util.MapUtils.entry;

/**
 * @author Neil Buesing
 */
public class MapInitializationTest {

  //the approach described in this blog
  private Map<String, Integer> mapA = MapUtils.asMap(entry("A", 1), entry("B", 2));

  //the approach described in this blog (unmodifiable)
  private Map<String, Integer> mapB = MapUtils.asUnmodifiableMap(entry("A", 1), entry("B", 2));
  
  //block initialization
  private Map<String, Integer> mapC = new HashMap<String, Integer>();
  {
    mapA.put("A", 1);
    mapA.put("B", 2);
  }

  //block initialization / unmodifiable
  private Map<String, Integer> mapD;
  {
    Map<String, Integer> map = new HashMap<String, Integer>();
    map.put("A", 1);
    map.put("B", 2);
    mapD = Collections.unmodifiableMap(map);
  }

  //inheritance with block initialization
  private Map<String, Integer> mapE = new HashMap<String, Integer>() {{
    put("A", 1);
    put("B", 2);
  }};

  //3rd party library Guava
  private Map mapF = ImmutableMap.builder().put("A", 1).put("B", 2).build();

  @Test
  public void test() {
    Assert.assertEquals(mapA, mapB);
    Assert.assertEquals(mapA, mapC);
    Assert.assertEquals(mapA, mapD);
    Assert.assertEquals(mapA, mapE);
    Assert.assertEquals(mapA, mapF);
  }

}