java - 在构造调用期间将 Java 枚举放入静态映射中是否安全？

Question

正如标题所示，我有以下Enum:

public enum MyEnum {

  FIRST_ENUM("first enum"),
  SECOND_ENUM("second enum"),
  THIRD_ENUM("third enum"),
  FORTH_ENUM("forth enum");

  private final String param;

  private static class Mapper {
    static Map<String, MyEnum> MAP = new HashMap<>();
  }

  MyEnum(String param) {
    this.param = param;
    Mapper.MAP.put(param, this); // Is this going to be a problem?
  }

  public static MyEnum MyEnum(String value) {
    return Holder.MAP.get(value);
  }

}

我想知道放置一个尚未完成实例化/构造的枚举是否可能会导致问题？

Answer 1

您不需要创建单独的 Mapper 类。我们的用例也使用类似的东西。

public enum MyEnum {

    FIRST_ENUM("first enum"),
    SECOND_ENUM("second enum"),
    THIRD_ENUM("third enum"),
    FORTH_ENUM("forth enum");

    private final String param;
    private static final Map<String, MyEnum> MAP = new HashMap<>();
    static {

        for (final MyEnum myEnum : MyEnum.values()) {
            MAP.put(myEnum.param, myEnum);
        }
    }

    MyEnum(String param) {
        this.param = param;
    }

    @JsonCreator
    public static MyEnum myEnumMapper(String value) {
        return MAP.get(value);
    }

}