[FLINK-6897][cep] Re-add support for Java 8 lambdas in CEP library

[dawidwys]

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[kl0u]

Hi @dawidwys !

This branch seems to be broken (does not compile). In the Pattern class, the newly introduced:
public Pattern<T, F> where(SimpleCondition<F> condition) and public Pattern<T, F> or(SimpleCondition<F> condition) should declare their arguments as final.

And even if you fix this, then the NFATests are broken because the IterativeCondition is not serializable:

org.apache.flink.api.common.InvalidProgramException: The implementation of the IterativeCondition is not serializable. The object probably contains or references non serializable fields.

	at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:100)
	at org.apache.flink.cep.pattern.Pattern.where(Pattern.java:134)
	at org.apache.flink.cep.pattern.Pattern.where(Pattern.java:154)
	at org.apache.flink.cep.nfa.NFATest.testNFASerialization(NFATest.java:195)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:497)
	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.rules.TestWatcher$1.evaluate(TestWatcher.java:55)
	at org.junit.rules.RunRules.evaluate(RunRules.java:20)
	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$2.evaluate(ParentRunner.java:268)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:51)
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: java.io.NotSerializableException: org.apache.flink.cep.nfa.NFATest
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1184)
	at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
	at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
	at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
	at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
	at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
	at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
	at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
	at org.apache.flink.util.InstantiationUtil.serializeObject(InstantiationUtil.java:315)
	at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:81)
	... 27 more

[dawidwys]

Sorry for that. I tried fixing it and there are some serialization issues, if we change the IterativeCondition from abstract class to interface, so I don't think we can address it without providing a yet another type hierarchy for conditions. :(

I will close the PR for now.