Bael 8274 (#17065)

* jsonarry to hashmap

* update

* change modules

* jsonarray to hashmap

* rework

* change the hashmap datatype

Author: wynnteo

json-modules/gson-2/src/main/java/com/baeldung/gson/jsonarraytohashmap/JSONArrayToHashMapConverter.java

@@ -0,0 +1,53 @@
+package com.baeldung.gson.jsonarraytohashmap;
+
+import java.lang.reflect.Type;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonArray;
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParseException;
+import com.google.gson.JsonPrimitive;
+import com.google.gson.reflect.TypeToken;
+
+public class JSONArrayToHashMapConverter {
+    public static Map<String, Integer> convertUsingIterative (JsonArray jsonArray) {
+        Map<String, Integer> hashMap = new HashMap<>();
+        for (JsonElement element : jsonArray) {
+            JsonObject jsonObject = element.getAsJsonObject();
+            String type = jsonObject.get("name").getAsString();
+            Integer amount = jsonObject.get("age").getAsInt();
+            hashMap.put(type, amount);
+        }
+        return hashMap;
+    }
+
+    public static Map<String, Integer> convertUsingStreams (JsonArray jsonArray) {
+        return StreamSupport.stream(jsonArray.spliterator(), false)
+            .map(JsonElement::getAsJsonObject)
+            .collect(Collectors.toMap(
+                jsonObject -> jsonObject.get("name").getAsString(),
+                jsonObject -> jsonObject.get("age").getAsInt()
+            ));
+    }
+
+    public static Map<String, Integer> convertUsingGson(JsonArray jsonArray) {
+        Map<String, Integer> hashMap = new HashMap<>();
+        Gson gson = new Gson();
+        List<Map<String, Object>> list = new Gson().fromJson(jsonArray, List.class);
+        for (Map<String, Object> map : list) {
+            String type = (String) map.get("name");
+            Integer amount = ((Double) map.get("age")).intValue(); // Gson parses numbers as Double
+            hashMap.put(type, amount);
+        }
+        return hashMap;
+    }
+}

json-modules/gson-2/src/test/java/com/baeldung/gson/jsonarraytohashmap/JSONArrayToHashMapConverterUnitTest.java

@@ -0,0 +1,88 @@
+package com.baeldung.gson.jsonarraytohashmap;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import java.util.Map;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import com.google.gson.JsonArray;
+import com.google.gson.JsonObject;
+
+public class JSONArrayToHashMapConverterUnitTest {
+
+    private JsonArray jsonArray;
+    private JsonArray jsonArrayWithDuplicates;
+
+    @BeforeEach
+    void setUp() {
+        jsonArray = new JsonArray();
+
+        JsonObject jsonObject1 = new JsonObject();
+        jsonObject1.addProperty("name", "John Doe");
+        jsonObject1.addProperty("age", 35);
+        jsonArray.add(jsonObject1);
+
+        JsonObject jsonObject2 = new JsonObject();
+        jsonObject2.addProperty("name", "Mary Jenn");
+        jsonObject2.addProperty("age", 41);
+        jsonArray.add(jsonObject2);
+
+        jsonArrayWithDuplicates = new JsonArray();
+
+        JsonObject jsonObject3 = new JsonObject();
+        jsonObject3.addProperty("name", "John Doe");
+        jsonObject3.addProperty("age", 35);
+        jsonArrayWithDuplicates.add(jsonObject3);
+
+        JsonObject jsonObject4 = new JsonObject();
+        jsonObject4.addProperty("name", "John Doe");
+        jsonObject4.addProperty("age", 41);
+        jsonArrayWithDuplicates.add(jsonObject4);
+    }
+
+
+    @Test
+    void givenJsonArrayWithObjects_whenConvertUsingIterative_thenCorrectHashMap() {
+        Map<String, Integer> hashMap = JSONArrayToHashMapConverter.convertUsingIterative(jsonArray);
+
+        assertEquals(35, hashMap.get("John Doe"));
+        assertEquals(41, hashMap.get("Mary Jenn"));
+    }
+
+    @Test
+    void givenJsonArrayWithObjects_whenConvertUsingStreams_thenCorrectHashMap() {
+        Map<String, Integer> hashMap = JSONArrayToHashMapConverter.convertUsingStreams(jsonArray);
+
+        assertEquals(35, hashMap.get("John Doe"));
+        assertEquals(41, hashMap.get("Mary Jenn"));
+    }
+
+    @Test
+    void givenJsonArrayWithObjects_whenConvertUsingGson_thenCorrectHashMap() {
+        Map<String, Integer> hashMap = JSONArrayToHashMapConverter.convertUsingGson(jsonArray);
+
+        assertEquals(35, hashMap.get("John Doe"));
+        assertEquals(41, hashMap.get("Mary Jenn"));
+    }
+
+    @Test
+    void givenJsonArrayWithDuplicateKeys_whenConvertUsingIterative_thenLastValueWins() {
+        Map<String, Integer> hashMap = JSONArrayToHashMapConverter.convertUsingIterative(jsonArrayWithDuplicates);
+        assertEquals(41, hashMap.get("John Doe"));
+    }
+
+    @Test
+    void givenJsonArrayWithDuplicateKeys_whenConvertUsingStreams_thenLastValueWins() {
+        Map<String, Integer> hashMap = JSONArrayToHashMapConverter.convertUsingIterative(jsonArrayWithDuplicates);
+        assertEquals(41, hashMap.get("John Doe"));
+    }
+
+    @Test
+    void givenJsonArrayWithDuplicateKeys_whenConvertUsingGson_thenLastValueWins() {
+        Map<String, Integer> hashMap = JSONArrayToHashMapConverter.convertUsingGson(jsonArrayWithDuplicates);
+        assertEquals(41, hashMap.get("John Doe"));
+    }
+}