Console c = System.console();

Is c null?

Doc:

public static Console console()

Returns the unique Console object associated with the current Java virtual machine, if any.

Returns: The system console, if any, otherwise null.

Replace your code with:

    System.out.println("Enter an input string:");
    Scanner sc = new Scanner(System.in);
    String str = sc.nextLine();
    System.out.println("The input string is:");
    System.out.println(str);

The problem is that the Console class does not work in most Java IDEs due to the way they run your program. This (http://stackoverflow.com/questions/26470972/trying-to-read-from-console-java/26473083#26473083) stackoverflow post provides a more detailed explanation as to why it does not work if you are curious. If you compiled your program in Eclipse and ran it in a console manually then it would work fine. This means that you have to use alternative ways to print and get input when working in your IDE. To print you can use System.out instead of console like this: Java System.out.println("Text you want to be printed to console"); System.out also has a printf and print method just like the Console class, that works in the same way as the Console equivalents And to get input you can use the Scanner class like this: ```Java import java.util.Scanner; // Place this at the top of your code to import the Scanner Scanner scanner = new Scanner(System.in); // Write this in your method once String input = scanner.nextLine(); // Then use scanner.nextLine as a substitute for console.readLine ```

From the Javadoc:

Returns the unique Console object associated with the current Java virtual machine, if any.

If there is no console associated to the JVM, the pointed line is the call of a method on a null object, hence the exception.

How do you launch your application?

Whether a virtual machine has a console is dependent upon the underlying platform and also upon the manner in which the virtual machine is invoked. If the virtual machine is started from an interactive command line without redirecting the standard input and output streams then its console will exist and will typically be connected to the keyboard and display from which the virtual machine was launched. If the virtual machine is started automatically, for example by a background job scheduler, then it will typically not have a console.

If you want to read the username from the standard input, you could use this code:

try {
    System.out.print("Enter Username: ");
    InputStreamReader streamReader = new InputStreamReader(System.in);
    BufferedReader bufferedReader = new BufferedReader(streamReader);
    String username = bufferedReader.readLine();
} catch (IOException e) {
    e.printStackTrace();
}

This is probably because you're running your program in an IDE, which doesn't use the console. Your code would work in Workspaces, or if executed from the command line. As an alternative, you can use the Scanner class inside of your IDE. (Scanner scanner = new Scanner(System.in); note that you have to print a separate prompt message (if needed) before using e.g. the .nextLine() method for reading the input) https://teamtreehouse.com/community/null-pointer-exception-error-2 http://stackoverflow.com/questions/14439226/console-input-error-java-lang-nullpointerexception

Adding to what Adam stated, in Eclipse IDE, you can use System.out.printf instead of console.printf and it should be fine.

Hey Mike, This has to do with how you run the program. System.console() will return the console that is connected with it. The command line is itself a console, so when you run it from there that console will be automatically connected and thats what returns from System.console(). However if you run the program from an IDE, like IntelliJ the console will not connect automatically therefore that System.console() will return null. Which causes that error when you try to readLine() from it. To accomplish the same task from an IDE, you can use the scanner class, try... ```java import java.util.Scanner; public static void main(String[] args) { Scanner scanner = new Scanner(System.in); System.out.print("Enter you name: "); String name = scanner.nextLine(); System.out.print("Enter an adjective: "); String adjective = scanner.nextLine(); System.out.printf("%s is very %s", name, adjective); } ``` Alternatively if you run your code from the command line like how its done in the lesson with workspace, itll work

It has to be System.console(). You are not doing any other operation on an object that would cause a null pointer exception. And as @McDowell has pointed out, System.console() can return a null value

while(ir.readLine()!=null){
    //...
}

This already reads a line, so when you want to actually obtain the line you checked about you get the next one, instead. In the last case, that's null since there are no other lines left.

The check should actually be done with the hasNextLine method, defined for that check:

while(ir.hasNextLine()){
    //...
}

Every time you call readLine() it moves ahead in your file.

So on every loop you're actually reading 4 to 8 lines instead of 1. Once you run out of lines to read, readLine() returns null which causes the NullPointerException.

change your loop to:

while(true) {
    String str = bf.readLine();

    if(str == null) {
        break;
    }
    if(str.contains("A")){ 
        aList.add(Integer.parseInt(str.substring(3)));
    }
    ...

As to call readLine() only once per loop.

no need for int numLines = readLines(file); you'll know you're done when readLine() returns null.

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.

Are you running this from an IDE? If yes then that is the problem since System.console() is not available in an IDE environment.

Try running it from the console (Command Prompt / Terminal) and it should work fine.

Edit: Just tried in my console and it worked (see screenshot below)

Check that the result of calling readLine() is not null (empty). If you check, and cause it not to do anything if its empty, this will solve your issue!

If you are using any IDE for Groovy, the input / output console will not be available to you hence throwing null pointer exception so, you can use the following, If you are using Intellij enable groovy console from Tools -> groovy console for I/O.

 println "What is your name?"
 println "Your name is:"+System.in.newReader().readLine()