materias 也是一个数组，因此需要如下内容：

JSONArray materias = obj.getJsonArray("materias");
List<String> materiasList = materias.getValuesAs(String.class);

这不是类型安全的，因此需要确保数组只包含字符串值。
另外，如果您使用的是Java8，那么可以迭代这些值并手动存储它们( JsonArray 也是一个 Collection<JsonValue> )

首先要让你的json有效。

[{
        "name": "A114",
        "grupo": "DAW2",
        "tutor": 15,
        "materias": ["DWES", "DWEC", "IW", "DAW", "IE"]
    }]

其次，您可以尝试以下方法：

for (JsonElement rec : recs) {

    Aula datos = new Aula();

    JSONObject obj = rec.getAsJsonObject();
    String name = obj.get("name").getAsString();    
    //datos.setNombre(name);

    String grupo = obj.get("grupo").getAsString();
    //datos.setGrupo(grupo);

    int tutor = obj.get("tutor").getAsInt();

     JsonObject obj = rec.getAsJsonObject();
      JsonArray materias = obj.getAsJsonArray("materias");

          List<String> materiasList = new ArrayList<>();

for (JsonElement item:
                 materias) {
                materiasList.add(item.getAsString());
            }

}

快速创建满足您需求的短期测试实现：

String json = "[{ \"name\":\"A114\",\"grupo\": \"DAW2\",\"tutor\":15,\"materias\": [\"DWES\",\"DWEC\",\"IW\",\"DAW\",\"IE\"]}]";

    JSONArray objectArray = new JSONArray(json);

    for (int x = 0; x < objectArray.length(); x++) {
        JSONObject obj = objectArray.getJSONObject(x);

        System.out.println("Name: " + obj.get("name"));
        System.out.println("Grupo: " + obj.get("grupo"));
        System.out.println("Tutor: " + obj.get("tutor"));

        JSONArray materias = obj.getJSONArray("materias");
        for (int y = 0; y < materias.length(); y++) {
            System.out.println("Materia " + y + ": " + materias.get(y));
        }
    }

输出
姓名：a114 grupo:daw2导师：15材料0:dwes材料1:dwec材料2:iw材料3:daw材料4:ie

我相信json中数组的语法与文件中的不同。例如-包含简单元素数组的简单完整json将是：

{"contacts":[
      { "firstName":"John", "lastName":"Doe" },
      { "firstName":"Jen", "lastName":"Smith" },
      { "firstName":"David", "lastName":"Jones" }
    ]}

在文本中，可以指定一个数组，而不需要打开和关闭json“{”和“}”。此外，您还需要命名数组元素（上面示例中的“contacts”）。我认为您想要的是（我使用“arrayname”作为数组元素名）：

{"arrayName":[{ "name":"A114","grupo": "DAW2","tutor":15,"materias":["DWES","DWEC","IW","DAW","IE"] }, 
      { "name":"121","grupo": "DAW1","tutor":8,"materias":["PROGRA","BD","SIS","LM","FOL"] }, 
      { "name":"A112","grupo": "AUTO1","tutor":5 }, 
      { "name":"A127","grupo": "ASIR1","tutor":2 }, 
      { "name":"A114","grupo": "SMR2","tutor":11 }, 
      { "name":"A128","grupo": "ASIR2","tutor":9,"materias":["IAW","ABD","ASIS","SI","IE"] }, 
      { "name":"A125","grupo": "ADM2","tutor":12 } ] }