- an empty line will throw IllegalArgumentException
- the decorator pattern is used
- covered by tests (JUnit5 and mockito)
hello world!
"h" - 1
"e" - 1
"l" - 3
"o" - 2
" " - 1
"w" - 1
"r" - 1
"d" - 1
"!" - 1
hello world!
"h" - 1
"e" - 1
"l" - 3
"o" - 2
" " - 1
"w" - 1
"r" - 1
"d" - 1
"!" - 1