procedure TForm2.Button1Click(Sender: TObject);
var sb: TStringBuilder;
  sw: TStringWriter;
  jtw: TJsonTextWriter;
  job: TJSONObjectBuilder;
begin
  sb := TStringBuilder.Create;
  sw := TStringWriter.Create(sb);
  jtw := TJsonTextWriter.Create(sw);
  jtw.Formatting := TJsonFormatting.Indented;
  job := TJSONObjectBuilder.Create(jtw);
  job
    .BeginObject
      .BeginArray(‘数组‘)
        .BeginObject.Add(‘id‘, 123)
          .Add(‘Name‘, ‘名称一‘)
          .AddNull(‘parent_id‘)
        .EndObject
      .EndArray
    .EndObject;
  Memo1.Text := sb.ToString;
  (*输出的json
{
    "数组": [
        {
            "id": 123,
            "Name": "名称一",
            "parent_id": null
        }
    ]
}
  *)
end;