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From Spark Shen <smallsmallor...@gmail.com>
Subject Re: [classlib][luni] JIRA 1492 Constructor of HashMap throw unexpected exception
Date Wed, 20 Sep 2006 01:20:00 GMT
Spark Shen 写道:
> Hi :
> Following is the discussion about JIRA 1492, shall we discuss it here?
>
> public class SubMapTest extends TestCase {
> public void testSubclass() {
> HashMap map = new HashMap();
> map.put("a", "a");
> SubMap map2 = new SubMap(map); // Harmony will throw an unexpected 
> exception here.
> }
> }
>
> class SubMap<K, V> extends HashMap<K, V> {
>
> public V put(K key, V value) {
> throw new RuntimeException();
> }
> }
>
>
> >Nathan Beyer
> >Harmony's behavior may be different in this case, but I'm not sure I 
> would consider this a valid issue. What's a real use case for this 
> type of sub-classing?
> [ Show » <http://issues.apache.org/jira/browse/HARMONY-1492> ]
> Nathan Beyer 
> <http://issues.apache.org/jira/secure/ViewProfile.jspa?name=nbeyer> 
> [18/Sep/06 08:41 PM] Harmony's behavior may be different in this case, 
> but I'm not sure I would consider this a valid issue. What's a real 
> use case for this type of sub-classing?
>
> <http://issues.apache.org/jira/secure/ViewProfile.jspa?name=spark+shen>>Spark

> Shen
> >What if change the RuntimeException to UnsupportedOperationException?
> [ Show » <http://issues.apache.org/jira/browse/HARMONY-1492> ]
> spark shen 
> <http://issues.apache.org/jira/secure/ViewProfile.jspa?name=spark+shen> 
> [18/Sep/06 08:48 PM] What if change the RuntimeException to 
> UnsupportedOperationException?
>
> >Alexey Petrenko
> >I'm not sure that this is a valid issue to.
> >As far as I understood the issue is that Harmony calls put method in 
> constructor while RI does not. Right?
>
> >If so I do not see any issue here.
>
I can not figure out what RI does. And please refer to JIRA 839, it 
reports similar use case.
My point here is
1. we may not be able to predict how users will use our library.
2. Users could guess our implementation w/o difficulty, which 
contradicts the encapulation priciple.
So I prefer to follow RI on this behavior.

When changing to UnsupportedOperationException, the use case is more 
practical, since it is highly like that put operation is not supported.
But it seems not so practical that this sub-hashMap can not be 
instantiated. May be one more assertion can convince you that this is bug.

public class SubMapTest extends TestCase {
public void testSubclass() {
HashMap map = new HashMap();
map.put("a", "a");
SubMap map2 = new SubMap(map);
assertEquals(1, map2.size());
}
}

class SubMap<K, V> extends HashMap<K, V> {
public SubMap(Map<? extends K, ? extends V> m) {
super(m);
}

public V put(K key, V value) {
throw new RuntimeException();
}
}

Best regards

-- 
Spark Shen
China Software Development Lab, IBM


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