[ 
https://issues.apache.org/jira/browse/FLINK-3444?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15228217#comment-15228217
 ] 

ASF GitHub Bot commented on FLINK-3444:
---------------------------------------

Github user zentol commented on a diff in the pull request:

    https://github.com/apache/flink/pull/1857#discussion_r58701074
  
    --- Diff: 
flink-java/src/main/java/org/apache/flink/api/java/ExecutionEnvironment.java ---
    @@ -777,7 +777,50 @@ public CsvReader readCsvFile(String filePath) {
                        throw new IllegalArgumentException("The number of 
elements must not be zero.");
                }
                
    -           return fromCollection(Arrays.asList(data), 
TypeExtractor.getForObject(data[0]), Utils.getCallLocationName());
    +           TypeInformation<X> typeInfo;
    +           try {
    +                   typeInfo = TypeExtractor.getForObject(data[0]);
    +           }
    +           catch (Exception e) {
    +                   throw new RuntimeException("Could not create 
TypeInformation for type " + data[0].getClass().getName()
    +                                   + "; please specify the TypeInformation 
manually via "
    +                                   + 
"StreamExecutionEnvironment#fromCollection(Collection, TypeInformation)");
    --- End diff --
    
    This should be ExecutionEnvironment#fromCollection


> env.fromElements relies on the first input element for determining the 
> DataSet/DataStream type
> ----------------------------------------------------------------------------------------------
>
>                 Key: FLINK-3444
>                 URL: https://issues.apache.org/jira/browse/FLINK-3444
>             Project: Flink
>          Issue Type: Bug
>          Components: DataSet API, DataStream API
>    Affects Versions: 0.10.0, 1.0.0
>            Reporter: Vasia Kalavri
>
> The {{fromElements}} method of the {{ExecutionEnvironment}} and 
> {{StreamExecutionEnvironment}} determines the DataSet/DataStream type by 
> extracting the type of the first input element.
> This is problematic if the first element is a subtype of another element in 
> the collection.
> For example, the following
> {code}
> DataStream<Event> input = env.fromElements(new Event(1, "a"), new SubEvent(2, 
> "b"));
> {code}
> succeeds, while the following
> {code}
> DataStream<Event> input = env.fromElements(new SubEvent(1, "a"), new Event(2, 
> "b"));
> {code}
> fails with "java.lang.IllegalArgumentException: The elements in the 
> collection are not all subclasses of SubEvent".



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