関連ワード:  java stream count occurrences    java stream count occurrences in list    java stream count matches    java stream count occurrences in string    java stream count occurrences in array    java 8 count occurrences in string    java 8 count occurrences in list    java 8 count occurrences of char in string    java stream map count occurrences    java 8 stream count occurrences in list