関連ワード:  java 8 counter    java 8 count occurrences in string    java 8 count frequency of characters in string    java 8 count number of occurrences in list    java 8 count characters in string    java 8 count words in string    java 8 count occurrences of char in string    java 8 count    java 8 count duplicates in list    java 8 increment counter in lambda