How to convert comma delimited String to List of T in Core Java

"first time long time" as they say on the radio talk shows...

I'm trying to parse a delimited property into a List. Simple enough, but for some reason I can't figure how to do this in a generic fashion using only Core Java. By generic, I mean the type of List to create may be a List< String >, List< Integer >, or List< Double >. My latest stab at it below give开发者_高级运维s runtime exceptions with non-Strings because I'm trying to cast from String to e.g. Double which is not allowed. Any help is appreciated.

public static <T> void parsePropsToList(String propName, String delim, List<T> listToFill){
   //This is paired down for convenience - assume getSplitList correctly parses to List<String>
   List<String> stringList = PropsManager.getSplitList(propName, delim);
   for(String s : stringList){
       listToFill.add((T)s);
   }
}

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You need to pass the Class in your function, something like;

public static <T> void parsePropsToList(
  String propName,
  String delim,
  List<T> listToFill,
  Class<T> clazz)

then using the reflection of clazz, get the Constructor having one String for its argument, split your propName with delim and, for each substring, invoke a new instance of T using the previous constructor. put this new instance into listToFill and return this list at then.

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Since Java throws out generic type information at runtime, you need to pass something in to your method that'll let you convert from the property string to the correct type.

I think the easiest thing to do would be to add a Parser parameter to your method:

public interface Parser<T> {
  public T parse(String value);
}

static <T> void parsePropsToList(String propName, String delim, List<T> listToFill, Parser<T> parser) {
  String value;
  //extract value from property
  listToFill.add(parser.parse(value));
}