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Scanner

Learn to read input with Scanner.

Scanner: console input

In Java, the Scanner class reads input from the console. First import java.util.Scanner, then connect it to System.in.

import java.util.Scanner;
Scanner input = new Scanner(System.in);
String name = input.nextLine();
System.out.println("Hello " + name);

Scanner can read text and numbers line by line or as space-separated tokens. It is good practice to print a question message before reading, so the user knows what to enter. When you are done, call close() to release the resource.

Release the resource with close

Scanner wraps a resource; when you are done, close() releases it. This is not critical in small console programs, but it matters when reading files.

Scanner input = new Scanner(System.in);
String line = input.nextLine();
System.out.println(line);
input.close();

For console input, close() also closes System.in; you cannot read again in the same program. So in console programs, closing is usually left to the end. When reading files, closing the resource right away prevents memory leaks.

Practice Greet the user

Create a Scanner, read the user's name and greet them as Hello, <name>. The user will type Ayşe.

Starter code

Main.java
import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    // Create a Scanner, read the name and greet
  }
}

Sample solution

Main.java
Scanner input = new Scanner(System.in);
System.out.print("Ad: ");
String name = input.nextLine();
System.out.println("Merhaba, " + name);

Expected output

Ad: Merhaba, Ayşe

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Which import is needed to use Scanner?

  • import java.io.Scanner;
  • import java.lang.Scanner;
  • import java.util.Scanner; Correct answer
  • import java.net.Scanner;

Explanation: the Scanner class lives in the java.util package, so you import java.util.Scanner.

2 Match each Scanner method to its purpose

Term Meaning
nextLine() Reads whole line
nextInt() Reads integer
close() Closes resource
new Scanner(System.in) Binds to console

3 Bind Scanner to the console

Question 
Scanner input = new Scanner(System.____);
String name = input.nextLine();
Answer 
Scanner input = new Scanner(System.in);
String name = input.nextLine();

Explanation: System.in is the standard input stream (keyboard).

All lessons in Beginner

1 Java basics

  1. What is Java?
  2. The main method
  3. Comments
  4. Class skeleton
  5. javac and java
  6. Summary - Java basics

2 Variables

  1. int and double
  2. boolean
  3. String
  4. Naming variables
  5. final variables
  6. Summary - Variables

3 Data types

  1. Primitive types
  2. Type casting
  3. String concatenation
  4. Math class
  5. BigInteger and BigDecimal
  6. Summary - Data types

4 Project: Calculator

  1. Project design
  2. Add/subtract
  3. Multiply/divide
  4. Error handling
  5. Putting it together

5 Operators

  1. Arithmetic
  2. Comparison
  3. Logical
  4. Bitwise
  5. Assignment and increment
  6. Summary - Operators

6 String basics

  1. length and charAt
  2. equals and equalsIgnoreCase
  3. indexOf and substring
  4. toUpperCase and trim
  5. String.format
  6. Summary - String basics

7 Conditionals

  1. The if statement
  2. else and else if
  3. Nested if
  4. switch
  5. Ternary
  6. Summary - Conditionals

8 Loops

  1. The for loop
  2. The while loop
  3. do-while
  4. break and continue
  5. for-each
  6. Summary - Loops

9 Project: Shopping cart

  1. Cart design
  2. Adding items
  3. Calculating totals
  4. Updating quantity
  5. Putting it together

10 Arrays

  1. Declaring arrays
  2. Array access
  3. Filling arrays
  4. Multi-dimensional arrays
  5. Copying arrays
  6. Summary - Arrays

11 Array methods

  1. Arrays.sort
  2. Arrays.toString
  3. Arrays.binarySearch
  4. Arrays.copyOf
  5. Arrays.fill
  6. Summary - Array methods

12 Collections

  1. ArrayList
  2. add and get
  3. HashMap
  4. put and get
  5. HashSet
  6. Summary - Collections

13 Methods

  1. Defining methods
  2. return
  3. void methods
  4. Method overloading
  5. Scope
  6. Summary - Methods

14 Method parameters

  1. Primitive parameters
  2. Object parameters
  3. varargs
  4. Multiple values via array
  5. final parameters
  6. Summary - Method parameters

15 Project: To-do CLI

  1. Task model
  2. Adding tasks
  3. Listing tasks
  4. Completing tasks
  5. Putting it together

16 String builder

  1. StringBuilder
  2. append
  3. insert and delete
  4. reverse
  5. toString
  6. Summary - String builder

17 Input and output

  1. Scanner
  2. nextInt and nextLine
  3. System.out.printf
  4. BufferedReader
  5. try-with-resources
  6. Summary - Input and output

18 Enum

  1. Declaring enums
  2. values and valueOf
  3. Enum fields
  4. Enum methods
  5. switch with enum
  6. Summary - Enum

19 Exception basics

  1. try/catch
  2. finally
  3. throw
  4. Exception hierarchy
  5. Multiple catch
  6. Summary - Exception basics

20 Beginner final

  1. Project design
  2. Data model
  3. Business logic
  4. Error handling
  5. Putting it together