Eclipse console

[S0m3guy]

Hey guys,

I just installed Oneiric Ocelot on my laptop and wanted to start programming in Java with Eclipse IDE.

But there is a little problem I got.


public class aufgabe7 {

public static void main(String[] args) {

System.out.println("Please input a number: ");

int zahl = Integer.parseInt(System.console().readLine());

}

}

For example with this code. When I run this, I get a NullPointerException because it does not let me input anything, it just runs through and then of course readLine() returns null.

I read that since Eclipse 3.2 or 3.3 there is something different with the intern console.

When I run that program with the terminal and the java commands everything works fine.

[11jmb]

add this to your code and see what happens



Console con = System.console();
if (con == null) {
System.err.println("Error:console is null");
System.exit(1);
}

[S0m3guy]

Gives me "Error: console is null"

[11jmb]

Ok. I believe that this is because the JVM you are using does not have an associated console. I don't think it is a problem specific to eclipse. There is another way to read input from the command line. try this:



BufferedReader reader = new BufferedReader(new InputStreamReader(System.in);

System.out.println("Please input a number: ");

int zahl = Integer.parseInt(reader.readLine());

[S0m3guy]

I know but if possible I would like to avoid those "Readers" since we don't use those in our lectures.

And before it worked fine as well :/

Which means I'd rather fix that JVM problem. I didn't install/fix/repair anything java specific after I installied Oneiric so I'm quite unsure what I got here and what I need.

[akoskm]

For such input actions (like starting program with specific parameters) you should inspect Run Configurations http://help.eclipse.org/galileo/index.jsp?topic=/org.eclipse.jdt.doc.user/tasks/tasks-java-local-configuration.htm .

[11jmb]

I know but if possible I would like to avoid those "Readers" since we don't use those in our lectures.

And before it worked fine as well :/

Which means I'd rather fix that JVM problem. I didn't install/fix/repair anything java specific after I installied Oneiric so I'm quite unsure what I got here and what I need.

Actually, I should ask before blaming the JVM, does this work when run from the command line instead of eclipse?

[S0m3guy]

The original code from first post, yes.

[akoskm]

The original code from first post, yes.

In this case you should definitely use run configurations...

[11jmb]

Well a few minutes of research is telling me that eclipse does not allow for use of the Console class. Perhaps somebody else here can help with a solution

I think your best option for this assignment is to just run for the command line, but in the future, I recommend using the Reader classes anyway, because Console is a newer feature, and the Readers give you some backwards compatibility.

[11jmb]

In this case you should definitely use run configurations...

This is not going to get the Console class working. This is just a way to pass in runtime arguments, like you would do from the command line. The only way that I can find to run the code from post 1 is to run it from the command line

[akoskm]

This is not going to get the Console class working. This is just a way to pass in runtime arguments, like you would do from the command line. The only way that I can find to run the code from post 1 is to run it from the command line

Yes, you are right, I misunderstood the problem. Sorry.

[S0m3guy]

But I dont understand why some time ago the same code worked fine within Eclipse and its console and now it just doesnt.

Maybe I should just switch to an older version of Eclipse -.-

Isnt there some way of getting Eclipse to start an external console when running a program?

[11jmb]

I'm not sure what to say. From my research, it looks like the reason is that eclipse is called by a javaw command which excludes a console. I was unable to find a good plugin or workaround but there obviously must be some way. Was this the same exact system where it worked before? (computer and eclipse install) If so, did you change anything (i.e. install a plugin) before it stopped working?

[ofnuts]

For what it's worth: https://bugs.eclipse.org/bugs/show_bug.cgi?id=122429

[S0m3guy]

I'm not sure what to say. From my research, it looks like the reason is that eclipse is called by a javaw command which excludes a console. I was unable to find a good plugin or workaround but there obviously must be some way. Was this the same exact system where it worked before? (computer and eclipse install) If so, did you change anything (i.e. install a plugin) before it stopped working?

Pretty much the same system, only thing that changed is that I installed a SSD and I installed a Eclipse completely new, so I guess a quite newer version.