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Date: Thu, 16 Mar 2006 22:31:59 +0800
From: Richard Liang <richard.liangyx@gmail.com>
Organization: IBM China Software Development Lab
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To: harmony-dev@incubator.apache.org
Subject: Re: Solution for 5.0 language features in Eclipse(Re: And enum types
 (Re: API with generics))
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That's great, Paulex. Then we can implement Java 5 language features for 
Harmony.

Oliver Deakin wrote:
> Paulex Yang wrote:
>> Hi,
>>
>> I just find a way to use Java 5 language features in Eclipse. You can 
>> set "Compiler compliance level" to 5.0, but set "Generated  .class 
>> files compatibility " to 1.4. So that most Java 5 language new 
>> features can be used, but the class file still can run on HarmonyVM!
>>
>
> That's great! I was suspicious that this would probably not work using 
> the javac provided with IBMs JDK, so I gave it a try:
>
>   >javac -source 1.5 -target 1.4 Java5Test.java
>   javac: source release 1.5 requires target release 1.5
>
> A little searching about turned up a message [1] in the Gump mail 
> archive that suggests using the "-target jsr14" option to compile
> 1.5 code into 1.4 compatible bytecodes. Attempting to compile 
> Java5Test.java with this option completes successfully.
> Having added your mocked-up Enum class to luni.jar I was able to run 
> Java5Test against Harmony code.
>
> Similar options can be passed to the Ant javac task:
>
>   <javac source="1.5" target="jsr14" ...>
>
> Regards,
> Oliver
>
> [1] 
> http://mail-archives.apache.org/mod_mbox/gump-general/200407.mbox/%3c40E5728E.70109@gmx.de%3e 
>
>
>
>> At least 6 Java 5 features can be used in this way, because they all 
>> don't need enhance class file (in same reason, I don't expect 
>> annotation can be used):
>>    generics
>>    enhance for loop
>>    enum
>>    static import
>>    auto boxing/unboxing
>>    varargs
>>
>> I've tested the 6 Java 5 language features in the little test below, 
>> and this class can run HarmonyVM smoothly. Only one modification 
>> needed, you should add a java.lang.Enum implementation to LUNI 
>> component, I've attached a naive impl of Enum below, too.
>>
>> But I haven't investigated the Eclipse compiler document yet to find 
>> what's the options should be set in command line, so that the Ant as 
>> well as Harmony build system can work in this way. If this is 
>> feasible, we can free from Java 1.4 jail!
>>
>> <code>
>> import static java.util.Locale.US;
>>
>> import java.util.ArrayList;
>> import java.util.HashMap;
>> import java.util.List;
>>
>> public class Java5Test {
>>    public static void main(String[] args) {
>>        List<String> slist = new ArrayList<String>();
>>        slist.add("generics and enhance for loop test");
>>        for(String s: slist){
>>            System.out.println(s);
>>        }
>>        System.out.println(EnumTest.enum1);
>>        variArgs(1,2,3);
>>        System.out.println("static import test:"+US);
>>        HashMap map = new HashMap();
>>        map.put(1, "value1");
>>        System.out.println("auto boxing/unboxing test:"+map.get(1));
>>    }
>>      enum EnumTest{
>>        enum1, enum2, enum3
>>    }
>>      public static void variArgs(int... i){
>>        System.out.println("variable args test");
>>    }
>> }
>> </code>
>>
>> <code>
>> package java.lang;
>>
>> public class Enum {
>>      public Enum(String name, int ordinal){
>>          }
>> }
>> </code>
>>
>> Mikhail Loenko wrote:
>>> Hi Paulex,
>>>
>>> We also had problem with enums while developing security package.
>>> Finally, we made it 1.5 compliant, tested with BEA 1.5 and commented 
>>> out
>>>
>>> See
>>> modules/security/src/common/javasrc/java/security/KeyRep.java
>>>
>>> Thanks,
>>> Mikhail
>>>
>>> 2006/3/15, Paulex Yang <paulex.yang@gmail.com>:
>>>  
>>>> Nathan Beyer wrote:
>>>>   
>>>>> My approach has been to make the APIs as close to possible as the 
>>>>> Java 5
>>>>> spec
>>>>>       
>>>> Agree.  Another issue is enum, for example,
>>>>
>>>> public enum SomeEnum{
>>>>    enum1, enum2, enum3
>>>> }
>>>>
>>>> I think the mimic will look like:
>>>>
>>>> public final class SomeEnum extends Enum{
>>>>    public static final SomeEnum enum1 =  new SomeEnum("enum1", 0);
>>>>    public static final SomeEnum enum2 = new SomeEnum("enum2", 1);
>>>>    public static final SomeEnum enum3 = new SomeEnum("enum3", 2);
>>>>
>>>>    protected SomeEnum(String name, int |ordinal|){
>>>>       super(name, ordinal).
>>>>    }
>>>> }
>>>>
>>>> and of course, the abstract class Enum(declaration without generics of
>>>> course) must exist at first.
>>>>
>>>> Thoughts?  I will raise a jira about Enum abstract class and create a
>>>> patch later to support this mimic if this approach is fine.
>>>>   
>>>>> and then leave //TODO comments about what needs to be added and 
>>>>> what is
>>>>> needed to fix it or what is preventing completion.
>>>>>
>>>>> The same condition applies to annotations and methods that take 
>>>>> advantage of
>>>>> return type covariance.
>>>>>
>>>>> We could consider creating a comment practice to flag specific 
>>>>> changes.
>>>>> Perhaps something like this:
>>>>>
>>>>> //HARMONY_GENERICS <Type> comment
>>>>> //HARMONY_ANNOTATION @annotation comment
>>>>> //HARMONY_COVARIANT_RETURN Type comment
>>>>>
>>>>> In Eclipse's Java editor you can add special meaning to comments of a
>>>>> certain format, so this could be taken advantage of there at least.
>>>>>
>>>>> -Nathan
>>>>>
>>>>> -----Original Message-----
>>>>> From: karan malhi [mailto:karan.malhi@gmail.com]
>>>>> Sent: Tuesday, March 14, 2006 8:04 PM
>>>>> To: harmony-dev@incubator.apache.org
>>>>> Subject: API with generics
>>>>>
>>>>> Hi,
>>>>>
>>>>> I might have missed out on it in earlier discussions so please 
>>>>> excuse me
>>>>> for my ignorance. What is the strategy of harmony with regards to
>>>>> Generics? To be more specific, I am right now implementing the
>>>>> javax.accessibility.AccessibleStateSet class which has a protected
>>>>> variable with the following signature:
>>>>>
>>>>>     protected Vector<AccessibleState> states
>>>>>
>>>>> My understanding is that currently generics are not supported. What
>>>>> should I do in this case? Should I just implement it without 
>>>>> generics?
>>>>> Is there a webpage where we are listing api methods/fields which 
>>>>> involve
>>>>> generics to later on update the code?
>>>>>
>>>>>
>>>>>       
>>>> -- 
>>>> Paulex Yang
>>>> China Software Development Lab
>>>> IBM
>>>>
>>>>
>>>>
>>>>     
>>>
>>>   
>>
>>
>


-- 
Richard Liang
China Software Development Lab, IBM