CODEWITHSUNDEEP
javaio
Enthusiastic
Enthusiastic

Reputation: 549

Console Input error java.lang.NullPointerException

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

Upvotes: 8

Views: 12108

Answers (5)

Petra Minaler
Petra Minaler

Reputation: 96

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

Upvotes: 0

chenna chennakesava
chenna chennakesava

Reputation: 1

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

Upvotes: 0

Alankar Srivastava
Alankar Srivastava

Reputation: 864

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.

Upvotes: 6

Rookie Programmer Aravind
Rookie Programmer Aravind

Reputation: 12154

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!

Upvotes: 3

Renato Lochetti
Renato Lochetti

Reputation: 4568

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.

Upvotes: 3

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