How to Use Google Gson to Convert a JSON Array into a HashMap

How can I convert a JSON array into a HashMap using Google Gson?

String jsonArray = "[{\"key1\": \"value1\", \"key2\": \"value2\"}, {\"key1\": \"value3\", \"key2\": \"value4\"}]"; 
Type listType = new TypeToken<List<Map<String, String>>>(){}.getType();
List<Map<String, String>> list = new Gson().fromJson(jsonArray, listType);

Google Gson is a powerful library that simplifies the process of converting Java objects to JSON and vice versa. This guide will demonstrate how to use Gson to parse a JSON array into a HashMap, which is a collection of key-value pairs in Java.

Gson gson = new Gson();
String jsonArray = "[{\"key1\": \"value1\", \"key2\": \"value2\"}, {\"key1\": \"value3\", \"key2\": \"value4\"}]";
Type listType = new TypeToken<List<Map<String, String>>>(){}.getType();
List<Map<String, String>> list = gson.fromJson(jsonArray, listType);

for (Map<String, String> map : list) {
    System.out.println(map.get("key1") + " - " + map.get("key2"));
} // Output each key-value pair

Causes

• Misunderstanding how JSON is structured when converting to a HashMap.
• Improper use of generic types when defining the object type for Gson.

Solutions

• Use the `TypeToken` class to define the type of the object expected.
• Ensure the JSON array is properly formatted as a string before parsing.

Mistake: Forgetting to provide the correct generic type when deserializing.

Solution: Always use `TypeToken` to specify the type you expect.

Mistake: Using non-string keys in the HashMap when JSON keys are strings.

Solution: Ensure all keys in the JSON match the expected format and types in the HashMap.