[jira] [Created] (FLINK-4793) Using a local method with :: notation in Java 8 causes index out of bounds

[Ted Dunning (JIRA)]

Ted Dunning created FLINK-4793:
----------------------------------

             Summary: Using a local method with :: notation in Java 8 causes 
index out of bounds
                 Key: FLINK-4793
                 URL: https://issues.apache.org/jira/browse/FLINK-4793
             Project: Flink
          Issue Type: Bug
            Reporter: Ted Dunning


I tried to use the toString method on an object as a map function:
{code}
                .<String>map(Trade::toString)
{code}
This caused an index out of bounds error:
{code}
java.lang.ArrayIndexOutOfBoundsException: -1
        at 
org.apache.flink.api.java.typeutils.TypeExtractor.getUnaryOperatorReturnType(TypeExtractor.java:351)
        at 
org.apache.flink.api.java.typeutils.TypeExtractor.getUnaryOperatorReturnType(TypeExtractor.java:305)
        at 
org.apache.flink.api.java.typeutils.TypeExtractor.getMapReturnTypes(TypeExtractor.java:120)
        at 
org.apache.flink.streaming.api.datastream.DataStream.map(DataStream.java:506)
        at 
com.mapr.aggregate.AggregateTest.testAggregateTrades(AggregateTest.java:81)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at 
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at 
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at 
org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
        at 
org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
        at 
org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
        at 
org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
        at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
        at 
org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
        at 
org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
        at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
        at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
        at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
        at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
        at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
        at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
        at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
        at 
com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:68)
{code}
On the other hand, if I use a public static method, like this:
{code}
                .<Trade>map(Trade::fromString)
{code}
All is good. fromString and toString are defined like this:
{code}
    public static Trade fromString(String s) throws IOException {
        return mapper.readValue(s, Trade.class);
    }

    @Override
    public String toString() {
        return String.format("{\"%s\", %d, %d, %.2f}", symbol, time, volume, 
price);
    }
{code}

This might be a viable restriction on what functions I can use, but there 
certainly should be a better error message, if so.



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