Reading integer input in Java - Cheat Sheet & Quick Revision

Recall & Review

beginner

What Java class is commonly used to read integer input from the user?

The <strong>Scanner</strong> class is commonly used to read integer input from the user in Java.

beginner

How do you create a Scanner object to read input from the keyboard?

You create it with: Scanner scanner = new Scanner(System.in);

beginner

Which Scanner method reads an integer value from the user?

The method nextInt() reads an integer value from the user.

intermediate

What happens if the user enters a non-integer value when using nextInt()?

An InputMismatchException is thrown because the input is not an integer.

intermediate

Why should you close the Scanner object after use?

Closing the Scanner frees system resources associated with it. Use scanner.close(); when done.

Which import statement is needed to use Scanner in Java?

A import java.io.Scanner;

B import java.input.Scanner;

C import java.lang.Scanner;

D import java.util.Scanner;

Scanner is part of the java.util package, so you import it with import java.util.Scanner;.

What does nextInt() do in Scanner?

A Reads the next integer from input

B Reads the next string from input

C Reads the next line from input

D Reads the next double from input

nextInt() reads the next integer value from the input.

How do you create a Scanner to read from the keyboard?

A Scanner scanner = new Scanner(System.out);

B Scanner scanner = new Scanner(System.in);

C Scanner scanner = new Scanner(System.err);

D Scanner scanner = new Scanner(System.input);

System.in represents keyboard input, so you create Scanner with new Scanner(System.in);.

What exception occurs if input is not an integer when calling nextInt()?

A InputMismatchException

B NullPointerException

C NumberFormatException

D IOException

If input is not an integer, Scanner throws InputMismatchException.

Why is it good practice to close a Scanner after use?

A To prevent syntax errors

B To clear the input buffer

C To free system resources

D To reset the Scanner object

Closing Scanner frees system resources like input streams.

Explain how to read an integer input from the user in Java using Scanner.

Think about the steps from importing Scanner to reading and closing it.

What should you do if the user enters invalid input when expecting an integer?

Consider how to handle errors gracefully when reading input.