Question

I am using Scanner class to take input. I am trying to get all the
words in a line using in.next(). I know it can be done using
nextLine() but i want to understand how in.next() and in.hasNext()
works.

System.out.println("What is designation");
        String desg = in.next();      
        while(in.hasNext()){
            desg+=in.next();      
        }

Gives out put as

What is designation
member technical staff\n
^Z
Hello abhishek kumarNext year you will be 22Salary is 30000.0Designation is membertechnicalstaff

But if i use

System.out.println("What is designation");
        String desg = in.next();      
        if(in.hasNext()){
            desg+=in.next();      
        }

It gives output as

What is designation
member technical staff
Hello abhishek kumarNext year you will be 22Salary is 44254.0Designation is membertechnical

In the first case i am getting all the words but it keeps asking for
next input and i have to specify end of input using CTRL+Z. But in
second case i am not getting the last word(staff). Please explain.

Answer 1

The first code reads the input in a while loop – i.e. until it finds in.hasNext() == false.

The second code is using an if condition – it reads in.next() at most once (after the initial read).

Thus, the second code is not “waiting for new input” because it simply asks for in.next() only once, and not until input is exhausted, unlike the second code snap.

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P.S. Note that the line String desg = in.next(); (in the first code snap) is a bad practice for two reasons:

1. It will fail for empty input.
2. It is a code duplication with the content of the while loop.