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Java Java Basics Getting Started with Java Strings and Variables

Posted by Sharad Shivmath
Sharad Shivmath
14,446 Points

Null pointer exception

Hi,

I am trying to run the same code in eclipse. I am getting the following error:

Exception in thread "main" java.lang.NullPointerException at <package_name>.Introductions.main(<line number>)

I had to use System.out.println() instead.

Thanks, Sharad

Kourosh Raeen
Kourosh Raeen
23,733 Points
Kourosh Raeen
Kourosh Raeen
23,733 Points

Hi Sharad - It would be hard to see what the problem is without seeing your code. Can you post it here?

Sharad Shivmath
Sharad Shivmath
14,446 Points 
package notDefault;

import java.io.Console;

public class Introductions {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Console console = System.console();     
        console.printf("Hello world");
    }

}

3 Answers

anil rahman
anil rahman
7,786 Points
anil rahman
anil rahman
7,786 Points

Use scanner for reading user input in ide's

Scanner input = new Scanner(System.in); //Scanner lets you read input

System.out.print("Enter a word\n"); //prompt them to type word
String word = input.nextLine(); //store the word they type in variable word

System.out.printf("Your word was: %s",word);
Sharad Shivmath
Sharad Shivmath
14,446 Points

Thanks a lot, that solves it.

The way I see it: It's sort of a work around, it works nonetheless. But, I really want to know how to debug the problem. What's the exact reason of the problem. Is it the version of Java? or something to do with the tool/environment setup? I think it's Java 8 on eclipse Mars 2.

Like you said earlier, the console.printf() function has 2 arguments, and the tutorial video leaves out the second argument, which works great in treehouse workspace, but does not in my system's eclipse. I think there is a difference in language version and setup environment/tool.

Thanks a lot though.

Seth Kroger
Seth Kroger
56,413 Points
Seth Kroger
Seth Kroger
56,413 Points

All have issues with java.io.Console with their built-in terminals. IDE's. They try to extend the I/O classes to intercept the terminal I/O but Console if declares as final, i.e., not extendable. System.out works virtually the same as Console for output but for input I suggest using BufferedReader because it has the same readLine() method:

BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
System.out.printf("Make a guess: ");
String guess = bufferedReader.readLine();

Note that printf() takes one or more arguments. The first argument is the format string, then enough to fill in the % placeholders in the format string. If the string has no % placeholders, it doesn't need a second arguemnt.

anil rahman
anil rahman
7,786 Points
anil rahman
anil rahman
7,786 Points

it's because you are using printf without giving it a variable.

I would just scrap using the console in an ide like eclipse and go with the usual way which is 

System.out.print("Hello World");

Or if you had variable then you can use printf also

String name = "World";
System.out.printf("Hello %s", name);
Sharad Shivmath
Sharad Shivmath
14,446 Points

Thanks, but I am already using System.out.<printfunc>. How do I readLine without console object in further lessons?