関連ワード:  unique characters in a string java 8    find unique characters in a string java 8    find unique characters in a string java 8 stream    first unique character in a string java 8    find distinct characters in a string java 8    duplicate characters in a string java 8    repeated characters in a string java 8    sort characters in a string java 8    remove duplicate characters in a string java 8    find repeated characters in a string java 8