Java How to get input from System console

Question

I am trying to use Console class to get input from user but a null object is returned when I call System console    Do I have to change anything before using System console   Console co System console    System out println co   try      String s co readLine

User · Answer

It will depend on your environment  If you re running a Swing UI via javaw for example  then there isn t a console to display  If you re running within an IDE  it will very much depend on the specific IDE s handling of console IO   From the command line  it should be fine though  Sample   import java io Console   public class Test        public static void main String   args  throws Exception           Console console   System console            if  console    null                System out println  Unable to fetch console                return                    String line   console readLine            console printf  I saw this line   s   line             Run this just with java    gt  javac Test java  gt  java Test Foo   lt ---- entered by the user I saw this line  Foo     lt ---- program output   Another option is to use System in  which you may want to wrap in a BufferedReader to read lines  or use Scanner  again wrapping System in

User · Answer

Try this  hope this will help       String cls0      String cls1       Scanner in   new Scanner System in         System out println  Enter a string          cls0   in nextLine           System out println  Enter a string          cls1   in nextLine

User · Answer

The following takes athspk s answer and makes it into one that loops continually until the user types  exit   I ve also written a followup answer where I ve taken this code and made it testable   import java io BufferedReader  import java io IOException  import java io InputStreamReader   public class LoopingConsoleInputExample       public static final String EXIT COMMAND    exit       public static void main final String   args  throws IOException         BufferedReader br   new BufferedReader new InputStreamReader System in          System out println  Enter some text  or      EXIT COMMAND      to quit           while  true              System out print   gt               String input   br readLine             System out println input             if  input length      EXIT COMMAND length    amp  amp  input toLowerCase   equals EXIT COMMAND                 System out println  Exiting                 return                       System out println     response goes here                        Example output   Enter some text  or  exit  to quit  gt  one one    response goes here     gt  two two    response goes here     gt  three three    response goes here     gt  exit exit Exiting

User · Answer

There are few ways to read input string from  your console keyboard  The following sample code shows how to read a string from the console keyboard by using Java   public class ConsoleReadingDemo    public static void main String   args                     BufferedReader reader   new BufferedReader new InputStreamReader System in        System out print  Please enter user name           String username   null      try           username   reader readLine          catch  IOException e            e printStackTrace              System out println  You entered       username                 In Java 5  Java util Scanner is used for this purpose      Scanner in   new Scanner System in       System out print  Please enter user name           username   in nextLine              System out println  You entered       username                   Java 6     Console console   System console        username   console readLine  Please enter user name              System out println  You entered       username          The last part of code used java io Console class  you can not get Console instance from System console   when running the demo code through Eclipse  Because eclipse runs your application as a background process and not as a top-level process with a system console

User · Answer

I wrote the Text-IO library  which can deal with the problem of System console   being null when running an application from within an IDE   It introduces an abstraction layer similar to the one proposed by McDowell  If System console   returns null  the library switches to a Swing-based console   In addition  Text-IO has a series of useful features    supports reading values with various data types  allows masking the input when reading sensitive data  allows selecting a value from a list  allows specifying constraints on the input values  format patterns  value ranges  length constraints etc      Usage example   TextIO textIO   TextIoFactory getTextIO     String user   textIO newStringInputReader            withDefaultValue  admin            read  Username     String password   textIO newStringInputReader            withMinLength 6           withInputMasking true           read  Password     int age   textIO newIntInputReader            withMinVal 13           read  Age     Month month   textIO newEnumInputReader Month class           read  What month were you born in      textIO getTextTerminal   println  User     user     is     age     years old               was born in     month     and has the password     password           In this image you can see the above code running in a Swing-based console

User · Answer

Scanner in   new Scanner System in    int i   in nextInt    String s   in next

User · Answer

Found some good answer here regarding reading from console  here another way use  Scanner  to read from console   import java util Scanner  String data   Scanner scanInput   new Scanner System in   data  scanInput nextLine     scanInput close                System out println data

User · Answer

Use System in  http   www java-tips org java-se-tips java util how-to-read-input-from-console html

User · Answer

Using Console to read input  usable only outside of an IDE    System out print  Enter something     String input   System console   readLine      Another way  works everywhere      import java io BufferedReader  import java io IOException  import java io InputStreamReader   public class Test       public static void main String   args  throws IOException            BufferedReader br   new BufferedReader new InputStreamReader System in            System out print  Enter String            String s   br readLine            System out print  Enter Integer             try               int i   Integer parseInt br readLine               catch NumberFormatException nfe                System err println  Invalid Format                         System console   returns null in an IDE  So if you really need to use System console    read this solution from McDowell

[java] Java: How to get input from System.console()

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