Latest build c572fa185d05 limitations

[Howard Lovatt]

I am contrasting:

  il.forEach( #( int i ) { 2 * i } );

which fails, however:

  il.forEach( #( int i ) {
     if ( i<  4 ) { throw new Exception(); }
     return i * i;
   } );

Works and yet both are #(int i) { ... }.

I also think people are used to interchanging Integer and int and
expect that boxing to take care of the details. So I think having to
say Integer will be confusing.

Cheers,

 -- Howard.

On 14 September 2010 13:47, Maurizio Cimadamore
<maurizio.cimadamore at oracle.com> wrote:
> On 12/09/10 21:38, Howard Lovatt wrote:
>>
>> It is odd that Integer works and int doesn't, the programmer will expect
>> that they are interchangeable. Even stranger is that:
>>
>>   il.forEach( #( int i ) {
>>     if ( i<  4 ) { throw new Exception(); }
>>     return i * i;
>>   } );
>>
>
> The problem here is that you are passing a lambda of the kind #(int x) where
> a Sam is expected, where the Sam declares a method accepting
> java.lang.Integer (not int). The spec is very clear in requiring the
> signature of the lambda to be override-equivalent w.r.t. the signature of
> the Sam method.
>
> Maurizio
>>
>> Works (note argument is an int).
>>
>>   -- Howard Lovatt +61 419 971 263 (sent from my PDA)
>>
>> On 11/09/2010, at 10:22 PM, Maurizio
>> Cimadamore<maurizio.cimadamore at oracle.com>  wrote:
>>
>>
>>>
>>> The problem has nothing to do with try/catch - it is caused by using
>>> 'int' as explicit type - if you replace it with Integer it works...
>>>
>>> Thanks for the report.
>>> Maurizio
>>>
>>> On 11/09/10 06:18, Howard Lovatt wrote:
>>>
>>>>
>>>> Hi,
>>>>
>>>> Using my usual source:
>>>>
>>>>     143: final IntList11 il = new IntList11();
>>>>     144: out.println( il );
>>>>     145: il.forEach( #( int i ) { 2 * i } ); // No exception; no try
>>>> block - needs type parameter
>>>>     146: out.println( il );
>>>>
>>>> Gives:
>>>>
>>>> Exception in thread "main" java.lang.VerifyError: Bad local variable
>>>> type in method
>>>> lambdas.Main$9.call(Ljava/lang/Integer;)Ljava/lang/Integer;
>>>> at offset 1
>>>>    at lambdas.Main.exceptionTransparency(Main.java:145)
>>>>    at lambdas.Main.main(Main.java:24)
>>>>
>>>> But:
>>>>
>>>>     try {
>>>>       il.forEach( #( int i ) {
>>>>         if ( i<   4 ) { throw new Exception(); }
>>>>         return i * i;
>>>>       } ); // Need to catch the checked exception!
>>>>     } catch ( final Throwable notUsed ) {
>>>>       out.println( "Exception caught 1" );
>>>>     }
>>>>     out.println( il );
>>>>
>>>> Works!
>>>>
>>>> And:
>>>>
>>>>   il.forEach( #( i ) { 2 * i } );
>>>>
>>>> Requires a try catch block (as before) and:
>>>>
>>>>   il.forEach( #( Integer i ) { 2 * i } );
>>>>
>>>> Works.
>>>>
>>>> Great to see such regular updates into the repository,
>>>>
>>>>   -- Howard.
>>>>
>>>>
>>>>
>>>
>>>
>
>



-- 
  -- Howard.