Gson toJson HashMap put

[ChiBenshuo]

Gson version 2.10.1

Java version 17

description

`
System.out.println(new Gson().toJson(new HashMap<String, String>() {{
put("a", "b");
}})); // print null

    String map2 = new Gson().toJson(new HashMap<String, String>() {{
        put("a", "b");
    }});
    System.out.println(map2); // print null

    Map<String, String> map = new HashMap<>();
    map.put("a", "b");
    System.out.println(new Gson().toJson(map)); // print {"a":"b"}

`

[eamonnmcmanus]

See #2023 and #298, among others. The short summary, to quote #298: "Don't use double brace initialization. It prevents serialization and Gson is designed for symmetric serialization and serialization."

Since you're using Java 17, Map.of or Map.ofEntries are much better alternatives.