How to get the user input in Java

Question

I attempted to create a calculator  but I can not get it to work because I don t know how to get user input   How can I get the user input in Java

User · Answer

import java util Scanner   public class Main       public static void main String   args            System out println  Welcome to the best program in the world              while  true                System out print  Enter a query                  Scanner scan   new Scanner System in               String s   scan nextLine                if  s equals  q                      System out println  The program is ending now                         break                else                    System out println  The program is running

User · Answer

You can use the Scanner class or the Console class  Console console   System console    String input   console readLine  Enter input

User · Answer

I like the following    public String readLine String tPromptString        byte   tBuffer   new byte 256       int tPos   0      System out print tPromptString        while true            byte tNextByte   readByte            if tNextByte    10                return new String tBuffer  0  tPos                      if tNextByte    13                tBuffer tPos    tNextByte                tPos                      and for example  I would do   String name   this readLine  What is your name

User · Answer

Here is how you can get the keyboard inputs   Scanner scanner   new Scanner  System in   System out print  Enter your name      name   scanner next       Get what the user types

User · Answer

Scanner input   new Scanner System in   String inputval   input next

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One of the simplest ways is to use a Scanner object as follows   import java util Scanner   Scanner reader   new Scanner System in       Reading from System in System out println  Enter a number      int n   reader nextInt       Scans the next token of the input as an int    once finished reader close

User · Answer

Here is a more developed version of the accepted answer that addresses two common needs    Collecting user input repeatedly until an exit value has been entered Dealing with invalid input values  non-integers in this example    Code  package inputTest   import java util Scanner  import java util InputMismatchException   public class InputTest       public static void main String args              Scanner reader   new Scanner System in           System out println  Please enter integers  Type 0 to exit              boolean done   false          while   done                System out print  Enter an integer                  try                   int n   reader nextInt                    if  n    0                        done   true                                    else                          do something with the input                     System out println   tThe number entered was      n                                               catch  InputMismatchException e                    System out println   tInvalid input type  must be an integer                     reader nextLine        Clear invalid input from scanner buffer                                  System out println  Exiting               reader close              Example  Please enter integers  Type 0 to exit  Enter an integer  12     The number entered was  12 Enter an integer  -56     The number entered was  -56 Enter an integer  4 2     Invalid input type  must be an integer  Enter an integer  but i hate integers     Invalid input type  must be an integer  Enter an integer  3     The number entered was  3 Enter an integer  0 Exiting      Note that without nextLine    the bad input will trigger the same exception repeatedly in an infinite loop   You might want to use next   instead depending on the circumstance  but know that input like this has spaces will generate multiple exceptions

User · Answer

This is a simple code that uses the System in read   function  This code just writes out whatever was typed  You can get rid of the while loop if you just want to take input once  and you could store answers in a character array if you so choose   package main   import java io IOException   public class Root           public static void main String   args                new Root               public Root                 while true                        try                               for int y   0  y  lt  System in available      y                                         System out print  char System in read                                                  catch IOException ex                                ex printStackTrace System out                   break

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Here  the program asks the user to enter a number  After that  the program prints the digits of the number and the sum of the digits   import java util Scanner   public class PrintNumber       public static void main String   args            Scanner scan   new Scanner System in           int num   0          int sum   0           System out println               Please enter a number to show its digits            num   scan nextInt             System out println               Here are the digits and the sum of the digits            while  num  gt  0                System out println     gt     num   10               sum    num   10              num   num   10                       System out println  Sum is     sum

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Just one extra detail   If you don t want to risk a memory resource leak  you should close the scanner stream when you are finished   myScanner close      Note that java 1 7 and later catch this as a compile warning  don t ask how I know that   -

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import java util Scanner   public class Myapplication       public static void main String   args            Scanner in   new Scanner System in            int a           System out println  enter              a   in nextInt             System out println  Number is      a

User · Answer

To read a line or a string  you can use a BufferedReader object combined with an InputStreamReader one as follows   BufferedReader bufferReader   new BufferedReader new InputStreamReader System in    String inputLine   bufferReader readLine

User · Answer

Here is your program from the question using java util Scanner   import java util Scanner   public class Example       public static void main String   args            int input   0          System out println  The super insano calculator            System out println  enter the corrosponding number             Scanner reader3   new Scanner System in           System out println               1  Add   2  Subtract   3  Divide   4  Multiply             input   reader3 nextInt             int a   0  b   0           Scanner reader   new Scanner System in           System out println  Enter the first number               get user input for a         a   reader nextInt             Scanner reader1   new Scanner System in           System out println  Enter the scend number               get user input for b         b   reader1 nextInt             switch  input               case 1   System out println a           b           add a  b                         break              case 2   System out println a     -     b           subtract a  b                         break              case 3   System out println a           b           divide a  b                         break              case 4   System out println a           b           multiply a  b                         break              default  System out println  your input is invalid                          break                       static int      add int lhs  int rhs    return lhs   rhs        static int subtract int lhs  int rhs    return lhs - rhs        static int   divide int lhs  int rhs    return lhs   rhs        static int multiply int lhs  int rhs    return lhs   rhs

User · Answer

import java util Scanner   public class userinput       public static void main String   args                    Scanner input   new Scanner System in            System out print  Name               String name   input next            System out print  Last Name               String lname   input next            System out print  Age               byte age   input nextByte             System out println                System out println                 System out println  Firt Name      name           System out println  Last Name      lname           System out println        Age      age

User · Answer

Can be something like this     public static void main String   args        Scanner reader   new Scanner System in        System out println  Enter a number          int i   reader nextInt        for  int j   0  j  lt  i  j            System out println  I love java

User · Answer

Keyboard entry using Scanner is possible  as others have posted  But in these highly graphic times it is pointless making a calculator without a graphical user interface  GUI    In modern Java this means using a JavaFX drag-and-drop tool like Scene Builder to lay out a GUI that resembles a calculator s console   Note that using Scene Builder is intuitively easy and demands no additional Java skill for its event handlers that what you already may have   For user input  you should have a wide TextField at the top of the GUI console    This is where the user enters the numbers that they want to perform functions on  Below the TextField  you would have an array of function buttons doing basic  i e  add subtract multiply divide and memory recall clear  functions  Once the GUI is lain out  you can then add the  controller  references that link each button function to its Java implementation  e g a call to method in your project s controller class   This video is a bit old but still shows how easy Scene Builder is to use

User · Answer

You can get user input using BufferedReader   BufferedReader br   new BufferedReader new InputStreamReader System in    String accStr     System out println  Enter your Account number      accStr   br readLine      It will store a String value in accStr so you have to parse it to an int using Integer parseInt   int accInt   Integer parseInt accStr

User · Answer

The most simple way to get user input would be to use Scanner  Here s an example of how it s supposed to be used   import java util Scanner  public class main   public static void main String  args    Scanner sc new Scanner System in   int a  String b  System out println  Type an integer here      a sc nextInt    System out println  Type anything here     b sc nextLine      The line of code import java util Scanner  tells the program that the programmer will be using user inputs in their code  Like it says  it imports the scanner utility  Scanner sc new Scanner System in   tells the program to start the user inputs  After you do that  you must make a string or integer without a value  then put those in the line a sc nextInt    or a sc nextLine     This gives the variables the value of the user inputs  Then you can use it in your code  Hope this helps

User · Answer

Scanner input new Scanner System in   int integer input nextInt    String string input next    long longInteger input nextLong

User · Answer

You can get the user input using Scanner  You can use the proper input validation using proper methods for different data types like next   for String or nextInt   for Integer    import java util Scanner   Scanner scanner   new Scanner System in      reads the input until it reaches the space System out println  Enter a string      String str   scanner next    System out println  str       str      reads until the end of line String aLine   scanner nextLine       reads the integer System out println  Enter an integer num      int num   scanner nextInt    System out println  num       num      reads the double value System out println  Enter a double      double aDouble   scanner nextDouble    System out println  double       aDouble       reads the float value  long value  boolean value  byte and short double aFloat   scanner nextFloat    long aLong   scanner nextLong    boolean aBoolean   scanner nextBoolean    byte aByte   scanner nextByte    short aShort   scanner nextShort     scanner close

User · Answer

import java util Scanner    class Daytwo      public static void main String   args           System out println  HelloWorld             Scanner reader   new Scanner System in           System out println  Enter the number              int n   reader nextInt            System out println  You entered     n

User · Answer

It is very simple to get input in java  all you have to do is   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

User · Answer

The best two options are BufferedReader and Scanner    The most widely used method is Scanner and I personally prefer it because of its simplicity and easy implementation  as well as its powerful utility to parse text into primitive data   Advantages of Using Scanner    Easy to use the Scanner class Easy input of numbers  int  short  byte  float  long and double  Exceptions are unchecked which is more convenient  It is up to the programmer to be civilized  and specify or catch the exceptions  Is able to read lines  white spaces  and regex-delimited tokens   Advantages of BufferedInputStream   BufferedInputStream is about reading in blocks of data rather than a single byte at a time Can read chars  char arrays  and lines Throws checked exceptions Fast performance Synchronized  you cannot share Scanner between threads      Overall each input method has different purposes     If you are inputting large amount of data BufferedReader might be better for you If you are inputting lots of numbers Scanner does automatic parsing which is very convenient   For more basic uses I would recommend the Scanner because it is easier to use and easier to write programs with  Here is a quick example of how to create a Scanner  I will provide a comprehensive example below of how to use the Scanner  Scanner scanner   new Scanner  System in      create scanner System out print  Enter your name             prompt user name   scanner next                           get user input    For more info about BufferedReader see How to use a BufferedReader and see Reading lines of Chars     java util Scanner  import java util InputMismatchException     import the exception catching class import java util Scanner     import the scanner class  public class RunScanner           main method which will run your program     public static void main String args                  create your new scanner            Note  since scanner is opened to  System in  closing it will close  System in               Do not close scanner until you no longer want to use it at all          Scanner scanner   new Scanner System in               PROMPT THE USER            Note  when using scanner it is recommended to prompt the user with  System out print  or  System out println          System out println  Please enter a number                use  try  to catch invalid inputs         try                   get integer with  nextInt                int n   scanner nextInt                  System out println  Please enter a decimal       PROMPT                get decimal with  nextFloat                float f   scanner nextFloat                  System out println  Please enter a word       PROMPT                get single word with  next                String s   scanner next                    ---- Note  Scanner nextInt   does not consume a nextLine character  n                 ---- In order to read a new line we first need to clear the current nextLine by reading it              scanner nextLine                    ----             System out println  Please enter a line       PROMPT                get line with  nextLine                String l   scanner nextLine                     do something with the input             System out println  The number entered was      n               System out println  The decimal entered was      f               System out println  The word entered was      s               System out println  The line entered was      l                       catch  InputMismatchException e                System out println   tInvalid input entered  Please enter the specified input                       scanner close       close the scanner so it doesn t leak             Note  Other classes such as Console and DataInputStream are also viable alternatives   Console has some powerful features such as ability to read passwords  however  is not available in all IDE s  such as Eclipse   The reason this occurs is because Eclipse runs your application as a background process and not as a top-level process with a system console  Here is a link to a useful example on how to implement the Console class   DataInputStream is primarily used for reading input as a primitive datatype  from an underlying input stream  in a machine-independent way  DataInputStream is usually used for reading binary data  It also provides convenience methods for reading certain data types  For example  it has a method to read a UTF String which can contain any number of lines within them   However  it is a more complicated class and harder to implement so not recommended for beginners  Here is a link to a useful example how to implement a DataInputStream

User · Answer

You can use any of the following options based on the requirements  Scanner class import java util Scanner         Scanner scan   new Scanner System in   String s   scan next    int i   scan nextInt      BufferedReader and InputStreamReader classes import java io BufferedReader  import java io InputStreamReader        BufferedReader br   new BufferedReader new InputStreamReader System in    String s   br readLine    int i   Integer parseInt s     DataInputStream class import java io DataInputStream        DataInputStream dis   new DataInputStream System in   int i   dis readInt     The readLine method from the DataInputStream class has been deprecated  To get String value  you should use the previous solution with BufferedReader  Console class import java io Console        Console console   System console    String s   console readLine    int i   Integer parseInt console readLine      Apparently  this method does not work well in some IDEs

User · Answer

class ex1           public static void main String args             int a  b  c          a   Integer parseInt args 0            b   Integer parseInt args 1            c   a   b          System out println  c       c              Output   javac ex1 java java ex1 10 20  c   30

User · Answer

You can get user input like this using a BufferedReader        InputStreamReader inp   new InputStreamReader System in       BufferedReader br   new BufferedReader inp          you will need to import these things    This is how you apply them      String name   br readline       So when the user types in his name into the console   String name  will store that information   If it is a number you want to store  the code will look like this       int x   Integer parseInt br readLine       Hop this helps

User · Answer

You can make a simple program to ask for user s name and print what ever the reply use inputs   Or ask user to enter two numbers and you can add  multiply  subtract  or divide those numbers and print the answers for user inputs just like a behavior of a calculator   So there you need 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 same way for the rest  Don t forget the import statement at the top of your code   Also see the blog post  Scanner class and getting User Inputs

User · Answer

Add throws IOException beside main    then  DataInputStream input   new DataInputStream System in   System out print  Enter your name    String name   input readLine

[java] How to get the user input in Java?

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