Enthuware

Which of the following expressions can be inserted in the above code so that the validateInput method will return true if and only if the input string contains non-whitespace data?

I understood the question as meaning "return true if the string contains any non-whitespace data". This means that if it should return true on, for example " t e s t " since it contains non-white space data.

Did you mean to ask "will return true if the input string contains non-whitespace data and only non-whitespace data?"

palmada wrote: ↑

Sun Apr 18, 2021 8:15 am

I understood the question as meaning "return true if the string contains any non-whitespace data". This means that if it should return true on, for example " t e s t " since it contains non-white space data.

Yes, you understood correctly. Yes, " t e s t " should return true.
The "only if" of the "if and only if" part is to convey that a string containing only whitespace data should not cause true to be returned.

>Did you mean to ask "will return true if the input string contains non-whitespace data and only non-whitespace data?"
No.

I think only should be after contains: "[...] will return true if the input string contains only non-whitespace data?"

If you frame it that way, it doesn't tell what should happen if the input stream does not contain only whitespace data.

I dont understand...

non-whitespace data = " x x x "

!str.isEmpty() -> " x x x " or " " -> FALSE, therefore, TRUE

!str.isBlank() -> " x x x " -> FALSE, therefore TRUE
!str.isBlank() -> " " -> TRUE, therefore FALSE

???? Accpding above, either Empty or Blank are TRUE??? Am I wrong?

Sorry, but I did not understand what exactly are you getting at. Please post the complete code that you are trying to run.

Hi,

The method isBlank() - Returns true if the string is empty or contains only white space codepoints, otherwise false.

For example:
String s = " ";

So, which variant is correct and why? :/
1 => [the input string contains non-whitespace data?]
or
2=> [the input string contains whitespace data?]

What difference is between non-whitespace and whitespace?

Thx.

"whitespace" means characters such as space, tab, new line. Non-whitespace means the opposite.
As per the problem statement, the validateInput(String str) method should return true if and only if the input string contains non-whitespace data. Meaning, the following strings should cause the validateInput method to return true:

"test" <- no whitspace at all

" t e s t " <- some whilespace but non-whitespace chars are also present

and the following strings should cause the validateInput method to return false:

"" <- empty string. Both isBlank and isEmpty will return true.

" " <- the string is not empty but there is no non-whitespace in this string. isBlank will return true but isEmpty() will return false, and !str.isEmpty() will be true, which is not what we want.


So, !str.isBlank() is the only correct option.

Hi, thank you very much for the answer! Now I understand.

I also answered incorrectly, because I had a problem interpreting the sentence in question

soncrash wrote: ↑

Wed Mar 29, 2023 8:28 am

I also answered incorrectly, because I had a problem interpreting the sentence in question

The same for me. It should really read "any non-whitespace data", because it is easy to interpret it as "only non-whitespace data" instead.