Java8 使用stream 实现wordcount

案例：

    public static void main(String[] args) {
        List<String> items = Arrays.asList("apple", "apple", "banana","apple", "orange",
                "banana", "papaya", "Hello","word","Hello","beijing","shanghai","china");

        /**
         * 使用 groupingBy和counting
         */
        Map<String, Long> wordCount = items
                .stream()
                .collect(Collectors.groupingBy(i -> i,Collectors.counting())
                );

        //无序结果
        System.out.println(wordCount);

        // 创建stream再次排序
        Map<String, Long> finalMap = new LinkedHashMap<>();
        wordCount.entrySet().stream()
                .sorted(Map.Entry.<String, Long>comparingByValue()
                        .reversed())
                .forEachOrdered(e -> finalMap.put(e.getKey(), e.getValue()));

        // 有序结果
        System.out.println(finalMap);
    }