Using Scanner class in Java - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the Scanner class in Java?

The Scanner class is used to read input from various sources like keyboard input, files, or strings. It helps to get user input easily.

beginner

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

You create it by writing: Scanner scanner = new Scanner(System.in); This connects the Scanner to the keyboard input.

beginner

Which method of Scanner reads a whole line of text including spaces?

The method nextLine() reads the entire line of input including spaces until the user presses Enter.

intermediate

What happens if you use nextInt() and then nextLine() without extra handling?

After nextInt(), the newline character remains in the input buffer. So nextLine() reads that leftover newline, often causing unexpected behavior.

intermediate

How do you properly close a Scanner object and why is it important?

You close it by calling scanner.close();. Closing frees system resources and avoids resource leaks, especially when reading from files.

Which import statement is needed to use the Scanner class?

A import java.Scanner.util;

B import java.util.Scanner;

C import java.lang.Scanner;

D import java.io.Scanner;

The Scanner class is in the java.util package, so you import it with import java.util.Scanner;.

What does scanner.nextInt() do?

A Reads the entire line as a string

B Reads the next word as a string

C Closes the scanner

D Reads the next integer from input

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

How can you read a single word (no spaces) from user input?

A Use <code>next()</code>

B Use <code>nextLine()</code>

C Use <code>nextWord()</code>

D Use <code>read()</code>

next() reads the next token (word) separated by whitespace.

What is a common problem when mixing nextInt() and nextLine()?

A <code>nextLine()</code> reads leftover newline causing skipped input

B The program crashes immediately

C Input is converted to uppercase automatically

D Scanner closes unexpectedly

After nextInt(), the newline character remains and nextLine() reads it, skipping user input.

Why should you close a Scanner reading from a file?

A To clear the input buffer

B To speed up the program

C To free system resources and avoid file locks

D It is not necessary to close Scanner

Closing Scanner frees resources and releases file locks, preventing resource leaks.

Explain how to use the Scanner class to read an integer and a full line of text from the keyboard.

Remember the leftover newline after reading numbers.

Describe why and how to close a Scanner object in Java.

Think about what happens if you leave files open.