Question

I have an enum like

public enum Field {
     A, B, C, D, E ....;

     private Field(){
     }
}

I have a class Panel that takes Field array to initialize the fields:

public class Panel {
     TextBox A; 
     TextBox B;
     TextBox C;
     TextBox D;
     TextBox E;
     ...


     public Panel(Field[] fields){
          this.fields = fields;
          init();
     }

     public void initA(){}
     public void initB(){}
     public void initC(){}
     public void initD(){}
     public void initE(){}
}

My question is, how can I initialize the fields that given without writing many if statement?

I can’t find any solution and I’m now initializing like this:

public void init(){
      for(int i = 0 ; i < fields.length; i++){
          if(fields[i] == Field.A){
              initA();
          } else if(fields[i] == Field.B){
              initB();
          } else if(fields[i] == Field.C){
              initC();
          } else if(fields[i] == Field.D){
              initD();
          } else if(fields[i] == Field.E){
              initE();
          }  ....
      }
}

Answer 1

Sounds like your design might need to be looked at. A few suggestions:

• Add the init method to your enum. So
  then you can iterate around the array
  of your enums and call the init
  method on it, so the enum knows how
  to do its own initialization
• create a Command object which does
  the initialization and create a
  Map of your enum as the key and
  the Command as the value. Cycle
  round the map running the Command
  for each enum.
• Use reflection – cost wise I wouldn’t be too concerned for this, unless your system is after incredibly low latency

For the first bullet, you could change the TextBox to hold a Field type against it e.g.

TextBox A = new TextBox(Field.A);
TextBox B = new TextBox(Field.B);

So if TextBox knows it is A,B,C,D,E then you just need to loop around your Field[] and when it finds its mathing TextBox run the init code (which can be stored against the specific enum instance). Of course you will need to register all your TextBox instances in a data structure somewhere, as you seem very set against using the very widely used reflection API.

In essence there has to be a link between the Field and the TextBox. Java cannot read your mind and know this without you telling it. Well, at least until Google unveil their telepathy API (and that would probably only be for Go…). This can be done based on naming (reflection), hardcoded logic (ifs or switches) or based on state. For the latter this means associating the Field with the TextBox, as I have demonstrated with the Constructor example above.