Question

我需要比较枚举，但请注意如何访问它们。我得到了一些字符串的直播活动。我需要将它与一组字符串进行比较以执行必要的操作。我试图使用枚举，但它无法正常工作

public enum Type {

    TYPE_ONE("event/one");
    TYPE_TWO("event/two");

    private Type(String mType){
        this.mType = mType;
    }
    private final String mType;

    public String getType(){return mType;}
}

我想在Switch / Case中进行比较：

 switch (event.getType()){
                                case Type.TYPE_ONE.getType():  // says "Constant expression required"
                                    Do something:
                                 case Type.TYPE_TWO.getType(): //  says "Constant expression required"
                                    Do something;
                            }

Answer 1

您希望抽象方法如何？

public enum Type {
    TYPE_ONE("event/one"){
        @Override
        public String getType(){return mType;}
    },
    TYPE_TWO("event/two"){
        @Override
        public String getType(){return mType;}
    };

    private final String mType;
    abstract public String getType();
    private Type(String mType){
        this.mType = mType;
    }
}

如果你想像下面这样使用String，我们需要使用JDK 7.当我们使用Java版本时，我们必须选择目标API 19（Kitkat）。

String hoge = "hoge";
switch (hoge) {
case "hoge":
  break;
default:
  break;
}

所以我建议你做以下几点;

Type type = Type.TYPE_TWO;
switch (type) {
case TYPE_ONE:
  break;
case TYPE_TWO:
  break;
default:
  break;
}

顺便说一下，这个方法可以这样访问;

Type type = Type.TYPE_TWO;
String strType = type.getType();
if (strType.equals("event/two")) {/*do something*/}

Answer 2

编辑你的枚举

public enum Type {

    TYPE_ONE("event/one");
    TYPE_TWO("event/two");

    private Type(String mType){
        this.mType = mType;
    }
    private final String mType;

    public String getType(){return mType;}

    //Provide the event type and get back the match Type enum
    public Type getTypeFromStringType(String type) {
       for (Type t : Type.values()) {
          if (type.equals(t.getType()) {
             return t;
          }
       }
       return null
    }
}

和你的方法

//You have to switch on an enum value
switch (getTypeFromStringType(event.getType())){
   case Type.TYPE_ONE; 
      break;
   case Type.TYPE_TWO;
      break;
}

在交换机情况下从Enum访问字符串

2 个答案: