Name: jl125535 Date: 04/08/2004


A DESCRIPTION OF THE REQUEST :
It is quite common requirement to dynamically return items according to their respective strings. e.g.

Object Example
{
  private Integer id;
  private String name;
  private Object value;

  public Object getProperty(String name)
  {
    if (name.equals("id")) {
       return this.id;
    }
    if (name.equals("name")) {
       return this.name;
    }
    if (name.equals("value")) {
       return this.value;
    }
   return null;
 }
}

This approach is very straightforward and works quite nicely for small amount of items. However, when the amount items increases:

- the performance remains linear (N/2)
- chained if statements look ugly
- with high number of items one is forced to create Map's with "binder" classes

There exists a simple and elegant solution; extended switch statement accepting Strings arguments:


  public Object getProperty(String name)
  {
    switch(name)
    {
    case "id":
       return this.id;

    case "name":
       return this.id;

    case "value":
       return this.id;
  
   default:
     return null;
   }
 }

javac would produce following (pseudo)code:

  public Object getProperty(String name)
  {
    switch(name.hashCode())
    case 0xd1b:
    {
      if (name.equals("id")) {
         return this.id;
      }
    }
    goto default;

   case 0x337a8b:
    {
      if (name.equals("name")) {
        return this.name;
      }
    }
   goto default;

  case 0x6ac9171:
   {
     if (name.equals("value")) {
       return this.value;
     }
   }
   goto default;

   default:
     return null;
   }
 }

For the String lookups this approach is fastest possible; "compile time hashtable".





JUSTIFICATION :
Given that the 1.5 is going to contain small features like autoboxing and enhanced for loop this enhancement would fit nicely to that bunch.
(Incident Review ID: 232974)
======================================================================