流和减少的Java 8编译器错误

梅尔兹

我正在编写一个小程序来生成一些随机数,并希望获得有关它们的统计信息。我有一个List<AtomicInteger>我想用来输出一些信息的。

我尝试使用以下代码将列表减少到总数(例如,所有AtomicIntegers的值之和):

// 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);

我的IDE(IntelliJ)对此行完全没有问题,但是对于我当前的javac版本(1.8.0_31),此行在编译器中导致NullPointerException:

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)

我知道可能还有其他方法可以实现相同的减少,但是我真的很想保留流的并行性质(因为我的原始代码有很多值)。谁能建议我另一个并行的reduce选项,它不会使我的编译器崩溃并且可以实现相同的结果?

我还想知道这是否只是我遇到的问题,或者其他人是否可以重现此编译器错误。

亚历克西斯C.

另外,reduce也可以使用mapToInt来代替使用sum

int total = values.stream().mapToInt(AtomicInteger::get).sum();

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