How to add and update map entry using Java Streams API

I just begin to learn Streams, and I have a task to count and sort all words in some array of String. I have already parsed my input to words, but I don't know how to add and update entry using the stream.

There is my parsing stream:

Stream<String> stringStream = lines.stream().flatMap(s -> Arrays.stream(s.split("[^a-zA-Z]+")));
        String[] parsed =  stringStream.toArray(String[]::new);

I have done this task without streams just like this:

Map wordToFrequencyMap = new HashMap<>();
for (String line: lines) {
    line=line.toLowerCase();
    String[] mas =  line.split("[^a-zA-Z]+");
    for (String word:mas) {
        if(word.length()>3) {
            if (!wordToFrequencyMap.containsKey(word)) {
                wordToFrequencyMap.put(word, new WordStatistics(word, 1));
            } else {
                WordStatistics tmp = wordToFrequencyMap.get(word);
                tmp.setFreq(tmp.getFreq() + 1);
            }
        }
    }
}

WordStatistics class:

public class WordStatistics implements Comparable<WordStatistics>{
    private String word;
    private int freq;

    public WordStatistics(String word, int freq) {
        this.word = word;
        this.freq = freq;
    }

    public String getWord() {
        return word;
    }

    public int getFreq() {
        return freq;
    }

    public void setWord(String word) {
        this.word = word;
    }

    public void setFreq(int freq) {
        this.freq = freq;
    }

    @Override
    public int compareTo(WordStatistics o) {
        if(this.freq > o.freq)
            return 1;
        if(this.freq == o.freq)
        {
            return -this.word.compareTo(o.word);
        }
        return -1;
    }
}