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Java 8 compiler error with thread and abbreviation

I am writing a small program to generate some random numbers and wanted to get statistical information about them. I have a List<AtomicInteger> that I want to use to output some information.

I tried using the following code to reduce the list to its total amount (for example, the sum of the values ​​of all AtomicIntegers):

 // not my real initialization code, just for illustration purposes List<AtomicInteger> values = new ArrayList<>(); for(int i = 0; i < 10; i++) { values.add(new AtomicInteger()); } // this is the problematic reduce int total = values .parallelStream() .reduce(0, (currentValue, currentAtomic) -> currentValue + currentAtomic.get(), (combiner1, combiner2) -> combiner1 + combiner2);

My IDE (IntelliJ) has no problems with this line, but with my current version of javac (1.8.0_31) this line leads to a NullPointerException in the compiler:

 An exception has occurred in the compiler (1.8.0_31). Please file a bug at the Java Developer Connection (http://java.sun.com/webapps/bugreport) after checking the Bug Parade for duplicates. Include your program and the following diagnostic in your report. Thank you. java.lang.NullPointerException at com.sun.tools.javac.code.Types.isConvertible(Types.java:290) at com.sun.tools.javac.comp.Check.assertConvertible(Check.java:922) at com.sun.tools.javac.comp.Check.checkMethod(Check.java:876) at com.sun.tools.javac.comp.Attr.checkMethod(Attr.java:3838) at com.sun.tools.javac.comp.Attr.checkIdInternal(Attr.java:3615) at com.sun.tools.javac.comp.Attr.checkMethodIdInternal(Attr.java:3522) at com.sun.tools.javac.comp.Attr.checkMethodId(Attr.java:3501) at com.sun.tools.javac.comp.Attr.checkId(Attr.java:3488) at com.sun.tools.javac.comp.Attr.visitSelect(Attr.java:3370) at com.sun.tools.javac.tree.JCTree$JCFieldAccess.accept(JCTree.java:1897) at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:607) at com.sun.tools.javac.comp.Attr.visitApply(Attr.java:1843) at com.sun.tools.javac.tree.JCTree$JCMethodInvocation.accept(JCTree.java:1465) at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:607) at com.sun.tools.javac.comp.Attr.attribExpr(Attr.java:649) at com.sun.tools.javac.comp.Attr.visitVarDef(Attr.java:1093) at com.sun.tools.javac.tree.JCTree$JCVariableDecl.accept(JCTree.java:852) at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:607) at com.sun.tools.javac.comp.Attr.attribStat(Attr.java:676) at com.sun.tools.javac.comp.Attr.attribStats(Attr.java:692) at com.sun.tools.javac.comp.Attr.visitBlock(Attr.java:1142) at com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:909) at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:607) at com.sun.tools.javac.comp.Attr.attribStat(Attr.java:676) at com.sun.tools.javac.comp.Attr.visitMethodDef(Attr.java:1035) at com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:778) at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:607) at com.sun.tools.javac.comp.Attr.attribStat(Attr.java:676) at com.sun.tools.javac.comp.Attr.attribClassBody(Attr.java:4342) at com.sun.tools.javac.comp.Attr.attribClass(Attr.java:4252) at com.sun.tools.javac.comp.Attr.attribClass(Attr.java:4181) at com.sun.tools.javac.comp.Attr.attrib(Attr.java:4156) at com.sun.tools.javac.main.JavaCompiler.attribute(JavaCompiler.java:1248) at com.sun.tools.javac.main.JavaCompiler.compile2(JavaCompiler.java:901) at com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:860) at com.sun.tools.javac.main.Main.compile(Main.java:523) at com.sun.tools.javac.main.Main.compile(Main.java:381) at com.sun.tools.javac.main.Main.compile(Main.java:370) at com.sun.tools.javac.main.Main.compile(Main.java:361) at com.sun.tools.javac.Main.compile(Main.java:56) at com.sun.tools.javac.Main.main(Main.java:42)

I know that there are probably other ways to achieve the same reduction, but I would very much like to keep the stream parallel (since my source code has many values). Can someone suggest me another option for parallel reduction, which will not destroy my compiler and cannot achieve the same result?

I would also like to know if this is just a problem that I am facing, or if other people can reproduce this compiler error.

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2 answers

Alternatively, instead of reduce you can use mapToInt and sum :

 int total = values.stream().mapToInt(AtomicInteger::get).sum();
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Version that does not break the compiler:

 // not my real initialization code, just for illustration purposes List<AtomicInteger> values = new ArrayList<>(); for(int i = 0; i < 10; i++) { values.add(new AtomicInteger()); } // this is the problematic reduce BiFunction<Integer, AtomicInteger, Integer> accumulator = (currentValue, currentAtomic) -> currentValue + currentAtomic.get(); BinaryOperator<Integer> combiner = (combiner1, combiner2) -> combiner1 + combiner2; int total = values .parallelStream() .reduce(0, accumulator, combiner);
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Source: https://habr.com/ru/post/983255/

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