Collectors.toMap IllegalStateException：在没有重复时可能出现重复键

Question

我一直在打这个错误，但我无法理解它，因为它抱怨只出现一次。

Exception in thread "main" java.lang.IllegalStateException: Duplicate key wp-admin/admin-ajax.php#13236 
at java.util.stream.Collectors.lambda$throwingMerger$0(Collectors.java:133) 
at java.util.HashMap.merge(HashMap.java:1245) 
at java.util.stream.Collectors.lambda$toMap$58(Collectors.java:1320) 
at java.util.stream.ReduceOps$3ReducingSink.accept(ReduceOps.java:169) 
at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193) 
at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1374) 
at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481) 
at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471) 
at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708) 
at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) 
at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499) 
at <my code> 

这是原来的代码：

reader.lines().filter(line -> line.startsWith(TAG_MAPPED_NODE)).map(line -> { 
    final String[] splitted = line.split(" "); 
    if (splitted.length != 3) 
     throw new IllegalStateException("Unexpected line: " + line); 
    return splitted;(splitted[1],splitted[2]); 
}).collect(Collectors.toMap(t -> t[1], t -> t[2])); 

然而，抱怨的价值究竟存在一次。输入验证码：

List<String> usefulLines = 
    reader.lines().filter(line -> line.startsWith(TAG_MAPPED_NODE)).collect(Collectors.toList()); 
List<String> trouble = 
    usefulLines.stream().filter(line -> line.contains("wp-admin/admin-ajax.php#13236")).collect(Collectors.toList()); 
System.out.println("Trouble size: " + trouble.size()); 
return usefulLines.stream().map(line -> { 
    final String[] splitted = line.split(" "); 
    if (splitted.length != 3) 
     throw new IllegalStateException("Unexpected line: " + line); 
    return splitted; 
}).collect(Collectors.toMap(t -> t[1], t -> t[2])); 

，输出为：Trouble size: 1

因此，有是有这个值只有一个入口（而且，我必须补充，我将其存储在地图的价值侧，不密钥）

系统配置：

• Java版本：OpenJDK的版本 “1.8.0_72”
• IDE：IntelliJ IDEA的2016.1
• OS版：Fedora 22的64位

所以在世界上为什么我得到那个异常？这看起来像一个JDK的bug - 任何人看到我做错了什么？

Answer 1

我的解决方案是用番石榴的ImmutableMap.toImmutableMap()来代替越野车Collectors.toMap()。好极了！