Console Input error java.lang.NullPointerException

Question

I have tried code:

import java.io.Console;
public class Default
{
    public static void main(String args[]) throws IOException
    {
        Console console = System.console();
        String testing = console.readLine("Enter Name: ");
        System.out.println("Entered Name: "+ testing);
    }
}

goes to exception with following error:
Source not found. NullPointerException

I am using Eclipse Juno EE for debugging .. !

And the reference link for above written code is here

Maybe [this](http://stackoverflow.com/questions/104254/java-io-console-support-in-eclipse-ide) question will help then. — MTCoster, Jan 21 '13 at 13:12
possible duplicate of http://stackoverflow.com/questions/4203646/system-console-returns-null http://stackoverflow.com/questions/4203646/system-console-returns-null — Shashi, Jan 21 '13 at 13:56
possible duplicate of [Masking password input from the console : Java](http://stackoverflow.com/questions/8138411/masking-password-input-from-the-console-java) — naXa stands with Ukraine, Aug 17 '15 at 14:53

score 6 · Accepted Answer · answered Jan 21 '13 at 13:06

6

Are you running your program from an ide as console.readLine returns null when used from an IDE.

For more details refer to this

If you run it from command line you will not get this error.

answered Jan 21 '13 at 13:06

Alankar Srivastava

844
5
18

In my case in Linux console when i run the script from run.sh i got `NullPointerException` after removing `"&"` from end of my script and remove `nohup` from the beginning the error gone away. good-luck – Saman Salehi Aug 07 '18 at 04:52

score 3 · Answer 2 · edited May 23 '17 at 11:46

3

System.console() returns null if there is no console.

You can work round this either by adding a layer of indirection to your code or by running the code in an external console and attaching a remote debugger.

edited May 23 '17 at 11:46

Community

1
1

answered Jan 21 '13 at 13:03

Renato Lochetti

4,558
3
32
49

1

Exactly - and, this is true when running from within Eclipse: https://bugs.eclipse.org/bugs/show_bug.cgi?id=122429 – Andreas Fester Jan 21 '13 at 13:04
I tried the same in netbeans, `System.console()` returns null even here. Why is it so? – Avinash Nair Jan 21 '13 at 13:06

score 3 · Answer 3 · answered Jan 21 '13 at 13:06

3

That is because, IDE is not using console !

Go to cmd.exe

type cd <bin path> hit enter..

now type java <classname> hit enter

It works!

answered Jan 21 '13 at 13:06

Rookie Programmer Aravind

11,952
23
81
114

Well, you're right. It works from windows console. But the problem here is, OP is using Eclipse IDE. And Eclipse IDE does not have a `System.console()`. It's a known bug: - https://bugs.eclipse.org/bugs/show_bug.cgi?id=122429 – Rohit Jain Jan 21 '13 at 13:11
@RohitJain, I said the same thing his IDE doesn't use console. But you can run any java compiled code from command prompt. That's the beauty of Java! – Rookie Programmer Aravind Apr 22 '14 at 13:39

score 0 · Answer 4 · edited Jun 24 '19 at 04:21

import java.io.*;

public class ConsoleExTest {

    public static void main(String[] args) throws Exception {
        Console c = System.console();
        String uname = c.readLine("User Name:");
        char[] pwd = c.readPassword("Password:");
        String upwd = new String(pwd);
        if (uname.equals("chenna") && upwd.equals("chenna")) {
            System.out.println("User is valid");
        } else {
            System.out.println("User is not valid");
        }
    }

}

Note:

System.console(); return null so we will get

score 0 · Answer 5 · answered Mar 17 '23 at 10:54

The cause of this problem has already been mentioned in other answers, but I would like to add one possible solution.

There is a library that can be used as a replacement for java.io.Console that mitigates the problem: https://codeberg.org/marc.nause/console-with-fallback

Console Input error java.lang.NullPointerException

5 Answers5

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