How can I read input from the console using the Scanner class in Java

Question

How could I read input from the console using the Scanner class  Something like this   System out println  Enter your username      Scanner   input       Or something like this  I don t know the code   Basically  all I want is have the scanner read an input for the username  and assign the input to a String variable

User · Answer

You can use the Scanner class in Java   Scanner scan   new Scanner System in   String s   scan nextLine    System out println  String      s

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You can flow this code   Scanner obj  new Scanner System in   String s   obj nextLine

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import java util Scanner   public class ScannerDemo       public static void main String   arguments           Scanner input   new Scanner System in            String username          double age          String gender          String marital status          int telephone number              Allows a person to enter his her name            Scanner one   new Scanner System in           System out println  Enter Name                username   one next            System out println  Name accepted     username               Allows a person to enter his her age            Scanner two   new Scanner System in           System out println  Enter Age                age   two nextDouble            System out println  Age accepted     age               Allows a person to enter his her gender           Scanner three   new Scanner System in           System out println  Enter Gender                gender   three next            System out println  Gender accepted     gender               Allows a person to enter his her marital status         Scanner four   new Scanner System in           System out println  Enter Marital status                marital status   four next            System out println  Marital status accepted     marital status               Allows a person to enter his her telephone number         Scanner five   new Scanner System in           System out println  Enter Telephone number                telephone number   five nextInt            System out println  Telephone number accepted     telephone number

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Scanner scan   new Scanner System in   String myLine   scan nextLine

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When the user enters his her username  check for valid entry also   java util Scanner input   new java util Scanner System in   String userName  final int validLength   6     This is the valid length of an user name  System out print  Please enter the username      userName   input nextLine     while userName length    lt  validLength            If the user enters less than validLength characters        ask for entering again     System out println            nUsername needs to be     validLength     character long         System out print   nPlease enter the username again          userName   input nextLine       System out println  Username is      userName

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Here is the complete class which performs the required operation   import java util Scanner   public class App       public static void main String   args            Scanner input   new Scanner System in           final int valid   6           Scanner one   new Scanner System in           System out println  Enter your username              String s   one nextLine             if  s length    lt  valid                System out println  Enter a valid username                System out println                   User name must contain     valid     characters                System out println  Enter again                  s   one nextLine                       System out println  Username accepted      s            Scanner two   new Scanner System in           System out println  Enter your age              int a   two nextInt            System out println  Age accepted      a            Scanner three   new Scanner System in           System out println  Enter your sex              String sex   three nextLine            System out println  Sex accepted      sex

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A simple example   import java util Scanner   public class Example       public static void main String   args                int number1  number2  sum           Scanner input   new Scanner System in            System out println  Enter First multiple            number1   input nextInt             System out println  Enter second multiple            number2   input nextInt             sum   number1   number2           System out printf  The product of both number is  d   sum

User · Answer

There is a simple way to read from the console   Please find the below code   import java util Scanner       public class ScannerDemo            public static void main String   args                Scanner sc   new Scanner System in                   Reading of Integer             int number   sc nextInt                    Reading of String             String str   sc next                      For a detailed understanding  please refer to the below documents   Doc  Now let s talk about the detailed understanding of the Scanner class working   public Scanner InputStream source        this new InputStreamReader source   WHITESPACE PATTERN       This is the constructor for creating the Scanner instance   Here we are passing the InputStream reference which is nothing but a System In  Here it opens the InputStream Pipe for console input   public InputStreamReader InputStream in        super in       try           sd   StreamDecoder forInputStreamReader in  this   String null         Check lock object           catch  UnsupportedEncodingException e               The default encoding should always be available         throw new Error e             By passing the System in this code will opens the socket for reading from console

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A simple example to illustrate how java util Scanner works would be reading a single integer from System in  It s really quite simple   Scanner sc   new Scanner System in   int i   sc nextInt      To retrieve a username I would probably use sc nextLine     System out println  Enter your username      Scanner scanner   new Scanner System in   String username   scanner nextLine    System out println  Your username is     username     You could also use next String pattern  if you want more control over the input  or just validate the username variable   You ll find more information on their implementation in the API Documentation for java util Scanner

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Reading Data From The Console   BufferedReader is synchronized  so read operations on a BufferedReader can be safely done from multiple threads  The buffer size may be specified  or the default size 8192  may be used  The default is large enough for most purposes   readLine      just reads data line by line from the stream or source  A line is considered to be terminated by any one these   n   r  or   r n Scanner breaks its input into tokens using a delimiter pattern  which by default matches whitespace  s  and it is recognised by Character isWhitespace      Until the user enters data  the scanning operation may block  waiting for input     Use Scanner BUFFER SIZE   1024  if you want to parse a specific type of token from a stream     A scanner however is not thread safe  It has to be externally synchronized   next         Finds and returns the next complete token from this scanner  nextInt      Scans the next token of the input as an int    Code  String name   null  int number   java io BufferedReader in   new BufferedReader new InputStreamReader System in    name   in readLine       If the user has not entered anything  assume the default value  number   Integer parseInt in readLine        It reads only String and we need to parse it  System out println  Name     name     t number     number    java util Scanner sc   new Scanner System in  useDelimiter    s    name   sc next        It will not leave until the user enters data  number   sc nextInt       We can read specific data  System out println  Name     name     t number     number       The Console class is not working in the IDE as expected  java io Console cnsl   System console    if  cnsl    null           Read a line from the user input  The cursor blinks after the specified input      name   cnsl readLine  Name          System out println  Name entered      name       Inputs and outputs of Stream  Reader Input      Output  Yash 777          Line1   Yash 777      7            Line1   7  Scanner Input     Output  Yash 777          token1   Yash                   token2   777

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import java util     class Ss       int id  salary      String name      void Ss int id  int salary  String name                this id   id          this salary   salary          this name   name             void display                 System out println  The id of employee     id           System out println  The name of employye     name           System out println  The salary of employee     salary            class employee       public static void main String args                  Scanner sc   new Scanner System in            Ss s   new Ss sc nextInt    sc nextInt    sc nextLine             s display

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You can make a simple program to ask for the user s name and print whatever the reply use inputs   Or ask the user to enter two numbers and you can add  multiply  subtract  or divide those numbers and print the answers for user inputs just like the behavior of a calculator   So there you need the Scanner class  You have to import java util Scanner   and in the code you need to use   Scanner input   new Scanner System in     input is a variable name   Scanner input   new Scanner System in    System out println  Please enter your name      s   input next       Getting a String value  System out println  Please enter your age      i   input nextInt       Getting an integer  System out println  Please enter your salary      d   input nextDouble       Getting a double   See how this differs  input next     i   input nextInt     d   input nextDouble     According to a String  int and a double varies the same way for the rest  Don t forget the import statement at the top of your code

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To read input   Scanner scanner   new Scanner System in   String input   scanner nextLine     To read input when you call a method with some arguments parameters   if  args length    2        System err println  Utilizare  java Grep  lt fisier gt   lt cuvant gt         System exit 1     try       grep args 0   args 1      catch  IOException e        System out println e getMessage

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There is problem with the input nextInt   method - it only reads the int value   So when reading the next line using input nextLine   you receive   n   i e  the Enter key  So to skip this you have to add the input nextLine     Try it like that    System out print  Insert a number       int number   input nextInt     input nextLine       This line you have to add  it consumes the  n character   System out print  Text1       String text1   input nextLine     System out print  Text2       String text2   input nextLine

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There are several ways to get input from the user  Here in this program we will take the Scanner class to achieve the task  This Scanner class comes under java util  hence the first line of the program is import java util Scanner  which allows the user to read values of various types in Java  The import statement line should have to be in the first line the java program  and we proceed further for code   in nextInt       It just reads the numbers  in nextLine       It get the String which user enters   To access methods in the Scanner class create a new scanner object as  in   Now we use one of its method  that is  next   The  next  method gets the string of text that a user enters on the keyboard   Here I m using in nextLine    to get the String which the user enters   import java util Scanner   class GetInputFromUser       public static void main String args              int a          float b          String s           Scanner in   new Scanner System in           System out println  Enter a string            s   in nextLine            System out println  You entered string     s            System out println  Enter an integer            a   in nextInt            System out println  You entered integer     a            System out println  Enter a float            b   in nextFloat            System out println  You entered float     b

[java] How can I read input from the console using the Scanner class in Java?

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