BAEL-586 guava multimap examples

guava19/src/test/java/com/baeldung/guava/MultimapTest.java

@@ -0,0 +1,62 @@
+package com.baeldung.guava;
+
+import com.google.common.collect.ArrayListMultimap;
+import com.google.common.collect.Multimap;
+import org.junit.Test;
+
+import java.util.LinkedHashMap;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.Assert.assertEquals;
+
+public class MultimapTest {
+
+    @Test
+    public void givenMap_whenAddTwoValuesFroSameKey_shouldOverridePreviousKey() {
+        //given
+        String key = "a-key";
+        Map<String, String> map = new LinkedHashMap<>();
+
+        //when
+        map.put(key, "firstValue");
+        map.put(key, "secondValue");
+
+        //then
+        assertEquals(1, map.size());
+    }
+
+    @Test
+    public void givenMultiMap_whenAddTwoValuesFroSameKey_shouldHaveTwoEntriesInMap() {
+        //given
+        String key = "a-key";
+        Multimap<String, String> map = ArrayListMultimap.create();
+
+        //when
+        map.put(key, "firstValue");
+        map.put(key, "secondValue");
+
+        //then
+        assertEquals(2, map.size());
+    }
+
+    @Test
+    public void givenMapOfListValues_whenAddTwoValuesFroSameKey_shouldHaveTwoElementInList() {
+        //given
+        String key = "a-key";
+        Map<String, List<String>> map = new LinkedHashMap<>();
+
+        //when
+        List<String> values = map.get(key);
+        if(values == null){
+            values = new LinkedList<>();
+            values.add("firstValue");
+            values.add("secondValue");
+        }
+        map.put(key, values);
+
+        //then
+        assertEquals(1, map.size());
+    }
+}