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User Input (Scanner) Review

User Input (Scanner) Review#

These questions are designed to assess your current understanding of using Scanners to read in user input!

Question 1 Which of the following code snippets shows the correct way to construct a Scanner that takes user input from the console?

  1. scanner input = new Scanner(System.in)

  2. Scanner input = Scanner(System.in)

  3. Scanner input = new Scanner(System.in);

  4. Scanner input = new Scanner();

See Answer

Option 3 is correct!

In order to create a Scanner, we must declare the Scanner type, give it a name, and have the correct Scanner construction code, which is = new Scanner(System.in);.

Question 2 How many tokens are listed below?

hello!          I love 
       computer        Science!
1 2 3

See Answer

8

Remember that tokens are any unit of input separated by white space (e.g. a space, tab, etc.).

Question 3 Which statement do we need at the very top of our program so that we can use Scanners?

  1. import java.util;

  2. import java.io.*;

  3. import java.util.*;

  4. import java.io;

See Answer

Option 3 is correct!

Question 4 What Scanner methods can you use to read in this token of user input? hello

Select all methods that could apply

  1. next()

  2. nextDouble()

  3. nextInt()

  4. nextLine()

  5. Error!

See Answer

Options 1 and 4 are correct!

The input hello can only be read as a string (“hello”). Trying to read in with nextInt() or nextDouble() would result in an exception, which is like an error.

Note: while both next() and nextLine() will read in this token of user input as a string, it’s better design to use the method that matches the input you expect closest. If you are expecting to only take in one token of user input, next() might be the best method to use here!

Question 5 What Scanner methods can you use to read in this token of user input? 3.0

Select all methods that could apply

  1. next()

  2. nextDouble()

  3. nextInt()

  4. nextLine()

  5. Error!

See Answer

Options 1, 2 and 4 are correct!

The input 3.0 can be read in as a double (3.0) or a String (“3.0”).

Question 6 What Scanner methods can you use to read in this token of user input? 3

Select all methods that could apply

  1. next()

  2. nextDouble()

  3. nextInt()

  4. nextLine()

  5. Error!

See Answer

Options 1, 2, 3, and 4 are correct!

The input 3 can be read in as an int (3), a double (3.0), or a String (“3”)!

Question 7 If I were to write a program to prompt the user asking them for their age, what Scanner method should I use to get that input?

Select all methods that could apply

  1. next()

  2. nextDouble()

  3. nextInt()

  4. nextLine()

See Answer

Options 4 is correct!

Since age is a value that is a whole number, we would want save that information as an int and use nextInt() to get that value.

nextDouble() could also work, but it’s not the best style: Because we typically represent age as a whole number, it would make the most sense to read that information in as an int.

Question 8 If I were to write a program to prompt the user asking them for their favorite season (e.g. winter, summer, autumn, or spring), what Scanner method should I use to get that input?

Select all methods that could apply

  1. next()

  2. nextDouble()

  3. nextInt()

  4. nextLine()

See Answer

Options 1 is correct!

Since a user’s favorite season will be one word, we should use next() to read in that single token as a String.