Introduction to Java Scanner Class

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Questions and Answers

What is the purpose of the Scanner class in Java?

To print results on the screen

To perform mathematical operations in the program

To allow the user to enter their own values at runtime (correct)

To hold hardcoded values in the program

Which version of Java introduced the Scanner class?

Java 5 (correct)

Java 8

Java 7

Java 3

What does 'import java.util.*;' do?

Imports all classes from the main package

Imports all classes from the java package

Imports all classes from the util package (correct)

Imports all classes from the Scanner package

Why do we need to import java.util.Scanner;?

To allow us to use the Scanner class in our program Signup and view all the answers

What is the problem with the initial Add2Numbers program?

It always displays 'total = 43' on the screen Signup and view all the answers

What does the asterisk * signify in 'import java.util.*;'?

All classes from the util package are imported Signup and view all the answers

What should be passed to the Scanner constructor to read input from the keyboard?

System.in Signup and view all the answers

Which method is used to read in an integer using the Scanner class?

nextInt() Signup and view all the answers

What method is used to read a line up until it reaches a white space using the Scanner class?

next() Signup and view all the answers

Which method is used to read a line (up until it reaches return) using the Scanner class?

nextLine() Signup and view all the answers

How can a value be assigned to a String object in Java?

"String value" Signup and view all the answers

Which method is used to get the first character of a String input using the Scanner class?

charAt() Signup and view all the answers

What does System.out represent in Java?

Printer output stream Signup and view all the answers

What does the following code do: `firstName = new String();`?

Creates a new String object with default value Signup and view all the answers

What type of input does the Scanner class method 'nextDouble()' read?

Double value Signup and view all the answers

What does the following line of code do: `num1 = keyboardIn.nextInt();`?

Reads an integer and assigns it to 'num1' Signup and view all the answers

What is the purpose of 'import java.util.*;'?

To import all classes from java.util package Signup and view all the answers

What will be printed by the following code: `System.out.println(num1 + ' and ' + num2);`?

The values of num1 and num2 concatenated with ' and ' as a string Signup and view all the answers

Study Notes

Java Basics

The Scanner class in Java is used to get input from the user.

Importing Classes

import java.util.*; is used to import all classes from the java.util package, including the Scanner class.
The asterisk * in import java.util.*; is a wildcard that represents all classes in the package.
import java.util.Scanner; is used to import only the Scanner class.

Scanner Class

The Scanner class was introduced in Java 1.5.
To read input from the keyboard, new Scanner(System.in) should be passed to the Scanner constructor.
The nextInt() method is used to read an integer using the Scanner class.
The next() method is used to read a line up until it reaches a white space using the Scanner class.
The nextLine() method is used to read a line up until it reaches return using the Scanner class.

String Objects

A value can be assigned to a String object in Java using the new keyword, for example: firstName = new String();.

Input and Output

System.out represents the standard output stream in Java, used to print messages to the console.
The nextDouble() method is used to read a double value using the Scanner class.
The num1 = keyboardIn.nextInt(); line of code reads an integer from the keyboard and assigns it to num1.
The System.out.println(num1 + ' and ' + num2); line of code prints the values of num1 and num2 to the console.

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Description

Learn about the Scanner class in Java, which allows user input for a program to act on specific values. Explore how to use the Scanner class to add two numbers in a Java program.

Introduction to Java Scanner Class

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Questions and Answers

What is the purpose of the Scanner class in Java?