Downloaded generic 2.0 .
Yup, I'm quite new to generics, but it definitly lets me use all the additions, unlike the old compiler.
But I have two questions , and I think this may be as good a place to ask as any other-
1. Is there an API documnetation for tiger ?
2. why doesn't this work ? -

           Double myFunction( MyObject mo )
       {
        if(xyz) return myHashMap.get(mykey) // (A)
        else return -1.00 ; //(B)
       }
      

Where (A) : values in myHashMap are Double,Keys are members defined in enum .This line compiles but throw a run-time error .
I have to write

 Double d=myHashMap.get(mykey); return d;
       

(B)Does not compile .Shouldn't autoboxing take care of it?

 

 

Hmm..am not really sure what "autoboxing" means ..are you referring to auto upcasting or something ?

Well you would need to caste it (coz hashmap would store it as an object and not as a double..I mean the particular class information is lost).Hence when you are retrieving , you need to cast it properly or you declare the return type as Object.
And also when you are returning -1.00 , compiler will complain , coz it doesnt expect a primitive...but an object.

thx.

 

 

Hmm..am not really sure what "autoboxing" means ..are you referring to auto upcasting or something ?

Well you would need to cast it (coz hashmap would store it as an object and not as a double..I mean the particular class information is lost).Hence when you are retrieving , you need to cast it properly or you declare the return type as Object.
And also when you are returning -1.00 , compiler will complain , coz it doesnt expect a primitive...but an object.

thx.

 

 

we6junkie, with all due respect, you don't seem competent to answer questions in this particular forum. Read the documentation on generics and autoboxing - there are links one or two of the six or so most recent threads.

 

 

Hi Archivist,
No offence taken...perhaps I do need to look at those.
I shall do that...thanks for the advice.


Thx.

 

 

Well, the example below works for me. We can't really answer your question unless you show us how you declare your HashMap.

import java.util.*;
 
public class HashMapFun {
    Map<String, Double> m_map = new HashMap<String,Double>();
 
    HashMapFun() {
        m_map.put("One", 1.0d);
        m_map.put("Two", 2.0d);
 
        System.out.println(getValue("Two"));
        System.out.println(getValue("One"));
    }
    
    Double getValue(String a_key) {
        if ("Two".equals(a_key) ) {
            return m_map.get(a_key);
        } else {
            //surprise!
            return new Double(3.0d);
        }
    }
 
    public static void main(String[] argv) {
        new HashMapFun();
    }
}

I do think you're expecting too much from autoboxing. I believe its only specified to work in certain places. Then again: why is that? It'll only serve to confuse people. I don't see why

    return 3.0d;

Shouldn't work in the above example?

 

 

Hi ,
Thanks all , specially The Lord.
Yeah , I went through almost whole of the forums and tried to put the bits togather . Not everything goes well with the compiler yet.
To start with , it seems auto-Unboxing doesn't work yet .So I better forget
abt. a few things.
However, I'd like to know this -
Is return -1.00d not a case of autoboxing , and only Map.put("Three",3) is ?

Also, I'm still looking for something like an API for generics .

PS- Sorry for my late response.It's partly due to the time-lag.
Thanks again.

 

 

Also , the Hashmap is simply
Hashmap<MyObjectType,Integer>= new Hashmap<MyObjectType,Integer>();
-rahul

 

 

No, because we don't yet have a generics-enabled javadoc.
However, with the 2.0 prototype we ship the sources for
the APIs. Look at them!


Boxing and unboxing are only implemented as argument
conversion in this prototype.

 

 

Thanks , Gafter.
Can't give the dukes to you, though, I think.Won't be "Officially Correct " for you,it seems.
Thanks to everyone again.
-Rahul

 

 

Incidentally, although Sun doesn't have a generics-compatible javadoc, SinjDoc does exist and is exactly such a thing. So you can generate the API docs yourself. SinjDoc doesn't yet support the new variance syntax or the JSR-201 features, but it will shortly. See http://cag.lcs.mit.edu/~cananian/Projects/GJ/

 

 

In the current prototype, boxing and unboxing are argument
conversions only.