In Java, how do I get the value of an enum inside the enum itself?

public enum Color {
    RED("R"),
    GREEN("G"),
    BLUE("B");

    private final String str;
    private Color(String s){
        str = s;
    }
    @Override
    public String toString() {
        return str;
    }
}

You can use constructors for Enums. I haven't tested the syntax, but this is the idea.

You can also switch on the type of this, for example:

public enum Foo { 
  A, B, C, D 
  ; 
  @Override 
  public String toString() { 
    switch (this) { 
      case A: return "AYE"; 
      case B: return "BEE"; 
      case C: return "SEE"; 
      case D: return "DEE"; 
      default: throw new IllegalStateException(); 
    } 
  } 
} 

Enum.name() - who'd of thunk it?

However, in most cases it makes more sense to keep any extra information in an instance variable that is set int the constructor.