小编Alf*_*iaz的帖子

我试图解析标准输入并提取与特定模式匹配的每个字符串,计算每个匹配的出现次数,并按字母顺序打印结果.这个问题似乎与Streams API很匹配,但是我找不到从Matcher创建匹配流的简洁方法.

我通过在匹配项上实现迭代器并将其包装到Stream中解决了这个问题,但结果不是很易读.如何在不引入其他类的情况下创建正则表达式匹配流？

public class PatternCounter
{
    static private class MatcherIterator implements Iterator<String> {
        private final Matcher matcher;
        public MatcherIterator(Matcher matcher) {
            this.matcher = matcher;
        }
        public boolean hasNext() {
            return matcher.find();
        }
        public String next() {
            return matcher.group(0);
        }
    }

    static public void main(String[] args) throws Throwable {
        Pattern pattern = Pattern.compile("[a-zA-Z0-9.!#$%&’*+/=?^_`{|}~-]+@[a-zA-Z0-9-]+(?:\\.[a-zA-Z0-9-]+)");

        new TreeMap<String, Long>(new BufferedReader(new InputStreamReader(System.in))
            .lines().map(line -> {
                Matcher matcher = pattern.matcher(line);
                return StreamSupport.stream(
                        Spliterators.spliteratorUnknownSize(new MatcherIterator(matcher), Spliterator.ORDERED), false);
            }).reduce(Stream.empty(), Stream::concat).collect(groupingBy(o -> o, counting()))
        ).forEach((k, v) -> { …