[2lists-to-map] Combining Two Lists into a Map in Java (#13484)

* [2lists-to-map] Combining Two Lists into a Map in Java

* [2lists-to-map] rename package

core-java-modules/core-java-collections-conversions-2/src/test/java/com/baeldung/combine2liststomap/CombineTwoListsInAMapUnitTest.java

@@ -0,0 +1,62 @@
+package com.baeldung.combine2liststomap;
+
+import static java.lang.Math.min;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+import org.junit.jupiter.api.Test;
+
+public class CombineTwoListsInAMapUnitTest {
+    private static final List<String> KEY_LIST = Arrays.asList("Number One", "Number Two", "Number Three", "Number Four", "Number Five");
+    private static final List<Integer> VALUE_LIST = Arrays.asList(1, 2, 3, 4, 5);
+    private static final Map<String, Integer> EXPECTED_MAP = new HashMap<String, Integer>() {{
+        put("Number One", 1);
+        put("Number Two", 2);
+        put("Number Three", 3);
+        put("Number Four", 4);
+        put("Number Five", 5);
+    }};
+
+    @Test
+    void givenTwoLists_whenUsingLoopAndListGet_shouldGetExpectedMap() {
+        Map<String, Integer> result = new HashMap<>();
+        int size = KEY_LIST.size();
+        if (KEY_LIST.size() != VALUE_LIST.size()) {
+            // throw an exception or print a warning
+            size = min(KEY_LIST.size(), VALUE_LIST.size());
+        }
+        for (int i = 0; i < size; i++) {
+            result.put(KEY_LIST.get(i), VALUE_LIST.get(i));
+        }
+        assertEquals(EXPECTED_MAP, result);
+    }
+
+    @Test
+    void givenTwoLists_whenUsingStreamApiAndListGet_shouldGetExpectedMap() {
+        Map<String, Integer> result = IntStream.range(0, KEY_LIST.size())
+          .boxed()
+          .collect(Collectors.toMap(KEY_LIST::get, VALUE_LIST::get));
+        assertEquals(EXPECTED_MAP, result);
+    }
+
+    @Test
+    void givenTwoLists_whenUsingIterators_shouldGetExpectedMap() {
+        Map<String, Integer> result = new HashMap<>();
+
+        Iterator<String> ik = KEY_LIST.iterator();
+        Iterator<Integer> iv = VALUE_LIST.iterator();
+        while (ik.hasNext() && iv.hasNext()) {
+            result.put(ik.next(), iv.next());
+        }
+
+        assertEquals(EXPECTED_MAP, result);
+    }
+
+}