Java enum对象详细编写

2019-03-15

简单demo实现

下方是一份简单的java代码。一般我们最简单的enum写法会是如下即可

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enum Fruit{
    Apple, Banana;
}

实际上这些Apple, Banana相当于是一个无参数的构造对象。如下想要运行有参数的构造对象，需要自己如下定义对应的构造方法。我们保证里面存了一个name和一个id。

import java.util.HashMap;
enum StreamCeommandType {
    UNSUPPORT_TYPE("UNSUPPORT TYPE", 0),
    START_STREAMJOB("START STREAMJOB", 1),
    STOP_STREAMJOB("STOP STREAMJOB", 2),
    CREATE_STREAMJOB("CREATE STREAMJOB", 3),
    DROP_STREAMJOB("DROP STREAMJOB", 4),
    START_APP("START APP", 5),
    STOP_APP("STOP APP", 6),
    CREATE_APP("CREATE APP", 7),
    DROP_APP("DROP APP", 8),
    USE_APP("USE APP", 9),
    LIST_STREAMJOBS("LIST STREAMJOBS", 10),
    SHOW_APP("SHOW APP", 11)
    ;
    private String name;
    int id;
    public static HashMap<String, StreamCeommandType> commands = new HashMap<String, StreamCeommandType>();
    static {
        commands.put("START STREAMJOB", START_STREAMJOB);
        commands.put("STOP STREAMJOB", STOP_STREAMJOB);
        commands.put("CREATE STREAMJOB", CREATE_STREAMJOB);
        commands.put("DROP STREAMJOB", DROP_STREAMJOB);
        commands.put("START APP", START_APP);
        commands.put("STOP APP", STOP_APP);
        commands.put("CREATE APP", CREATE_APP);
        commands.put("DROP APP", DROP_APP);
        commands.put("USE APP", USE_APP);
        commands.put("LIST STREAMJOBS", LIST_STREAMJOBS);
        commands.put("SHOW APP", SHOW_APP);
    };
    StreamCeommandType(String name, int id){
        this.name = name;
        this.id = id;
    }
    public int getValue(){
        return id;
    }
    @Override
    public String toString(){
        return String.valueOf(id) + " : " + name;
    }
    public static StreamCeommandType find(String name){
        if(name == null)
            return UNSUPPORT_TYPE;
        if(commands.containsKey(name))
            return commands.get(name);
        else return UNSUPPORT_TYPE;
    }
}
public class StreamCommandParser {
    public static void main(String [] args){
        System.out.println(StreamCeommandType.find("LIST STREAMJOBS"));
        System.out.println(StreamCeommandType.find("haha"));
    }
}

下方是个scala版本的类似实现

object UnkownCommandType extends Enumeration{
  type UnkownCommandType = Value
  val START_STREAMJOB = Value("start streamjob")
  val STOP_STREAMJOB = Value("stop streamjob")
  val CREATE_STREAMJOB = Value("create streamjob")
  val DROP_STREAMJOB = Value("drop streamjob")
  val START_APP = Value("start app")
  val STOP_APP = Value("stop app")
  val CREATE_APP = Value("create app")
  val DROP_APP = Value("drop app")
  val USE_APP = Value("use app")
  val LIST_JOBS = Value("list streamjobs")
  val UNSUPPORT_TYPE = Value("unsupport type")
  val arr$: Array[UnkownCommandType] = values.toArray
  val len$ = arr$.length
  //  arr$.foreach(x => println(x.toString) )
  lazy val commands: mutable.Map[String, UnkownCommandType] ={
    var commands = mutable.HashMap[String, UnkownCommandType]()
    arr$.foreach(x => commands.put(x.toString, x))
    commands
  }
  def find(command: Array[String]): Option[UnkownCommandType] = {
    if (null == command)
      Some(UNSUPPORT_TYPE)
    else{
      val cmd: String = command.length match {
        case 0 => ""
        case 1 => command(0).toLowerCase
        case _ => {
          if(command(1) == "application") command(0).toLowerCase + " " + "app"
          else (command(0) + " " + command(1)).toLowerCase
        }
      }
      if (commands.contains(cmd)) commands.get(cmd)
      else Some(UNSUPPORT_TYPE)
    }
  }
  def == (unkownCommandType: UnkownCommandType): Boolean ={
    toString == unkownCommandType.toString
  }
}