hadoop的入门程序，java8也能实现

txt统计单词数量程序

@Testpublic void fileWordCount() throws IOException {    //特殊文件需要格式转换为txt    Files.readAllLines(Paths.get("D:\\jd.txt"), StandardCharsets.UTF_8).parallelStream()            //将多个流融合为一个            .flatMap(line -> Arrays.stream(line.trim().split("\\s")))            .filter(word -> word.length() > 0)            .map(word -> new AbstractMap.SimpleEntry<>(word, 1))            .collect(groupingBy(AbstractMap.SimpleEntry :: getKey, counting()))            .entrySet().forEach(System.out :: println);}

List统计单词数量程序

@Testpublic void listWordCount(){    List
    
      stringList = Arrays.asList("a","b","c","a");    stringList.stream()            .map(s -> new AbstractMap.SimpleEntry<>(s, 1))            .collect(groupingBy(AbstractMap.SimpleEntry :: getKey, counting()))            .entrySet().stream()            .forEach(System.out :: println);    System.out.println("---------------------------------------------------");    //通过自定义reduce统计，其实counting（）也使用的是reduce    //记住：凡是在中间操作使用了map，接口定义都需要声明出来，直接使用lambda表达式会有1.无法读取method，2.类型检查不到 的问题    BinaryOperator
     
       binaryOperator2 = Integer::sum;    //排序的转换规则接口    ToIntFunction
      
        sortMapFunction = (Map.Entry se) -> Integer.valueOf(se.getValue().toString()).intValue();    stringList            .stream()            .map(s -> new AbstractMap.SimpleEntry<>(s, 1))            .collect(groupingBy(AbstractMap.SimpleEntry::getKey,                    reducing(0, AbstractMap.SimpleEntry::getValue,binaryOperator2)))            .entrySet()            .stream()            .sorted(Comparator.comparingInt(sortMapFunction))            .forEach(System.out::println);}