Read from console (Scanner Class)

[hey]

Hi, today is the second day I am trying to get familiar with Java..I'm trying to implement reading from console.. When I use this Input class once, everything is ok, if I try to read to integers, I get exceptions and errors.. Please, help!
This is a main program
import java.util.Scanner;
import Input.Input;
class Min{
public static void main(String[] args){
int x=0,y=0,z=0, f=0, i=0;

x = Input.InputInt();
System.out.println(x);
y = Input.InputInt();
System.out.println(x);


}
}
and Input class itself
package Input;
import java.util.Scanner;
public class Input{
public static int InputInt(){
int x=0;
Scanner in = new Scanner(System.in);

//reads int from the console
//and stores into x

x=in.nextInt();
in.close();
return x;


}

}

[staykovmarin]

You are getting that problem because InputInt() is static. That means that everything declared in that method is static, so it will be the same throughout execution. More on this: Understanding Instance and Class Members (The Java™ Tutorials > Learning the Java Language > Classes and Objects)

You are closing the Scanner stream in the InputInt()

Code:

in.close();

The problem is that once you close it, the stream is dead, so the next time you call it, it cant read from the command line (thats why it works on the first call of InputInt() but not the second.

One solution is to remove the in.close() and it will work fine. Another solution is the create an instance of the Input class and make InputInt non static:

Code:

import java.util.Scanner;

class Min {
	public static void main(String[] args) {
		int x = 0, y = 0, z = 0, f = 0, i = 0;
		Input input = new Input();
		
		x = input.InputInt();
		System.out.println(x);
		y = input.InputInt();
		System.out.println(x);
		
	}
}

class Input {
	public int InputInt() {
		int x = 0;
		Scanner in = new Scanner(System.in);

		// reads int from the console
		// and stores into x
		x = in.nextInt();

                // notice that now you can close the stream, since the method is non static
                in.close();

		return x;
	}

}

[hey]

Quote:

Originally Posted by staykovmarin

You are getting that problem because InputInt() is static. That means that everything declared in that method is static, so it will be the same throughout execution. More on this: Understanding Instance and Class Members (The Java™ Tutorials > Learning the Java Language > Classes and Objects)

You are closing the Scanner stream in the InputInt()

Code:

in.close();

The problem is that once you close it, the stream is dead, so the next time you call it, it cant read from the command line (thats why it works on the first call of InputInt() but not the second.

One solution is to remove the in.close() and it will work fine. Another solution is the create an instance of the Input class and make InputInt non static:

Code:

import java.util.Scanner;

class Min {
	public static void main(String[] args) {
		int x = 0, y = 0, z = 0, f = 0, i = 0;
		Input input = new Input();
		
		x = input.InputInt();
		System.out.println(x);
		y = input.InputInt();
		System.out.println(x);
		
	}
}

class Input {
	public int InputInt() {
		int x = 0;
		Scanner in = new Scanner(System.in);

		// reads int from the console
		// and stores into x
		x = in.nextInt();

                // notice that now you can close the stream, since the method is non static
                in.close();

		return x;
	}

}

Thanks a lot. I just removed in.close(), and it worked, on the other hand it doesn't work, when I make non-static (I just copied your code)

[staykovmarin]

Define doesnt work:

Code:

		x = input.InputInt();
		System.out.println(x);
		y = input.InputInt();
		System.out.println(x);

You are also printing x twice there.

[hey]

Quote:

Originally Posted by staykovmarin

Define doesnt work:

Code:

		x = input.InputInt();
		System.out.println(x);
		y = input.InputInt();
		System.out.println(x);

You are also printing x twice there.

Yes, I saw that))

Exception in Thread "main" java.util.NoSuchElementException
at ..
at ..
.. smth like that
after I enter the first value, it prints it and right after that I get that exception

[staykovmarin]

Post your current code (also a partial exception is really of no help).

I have a feeling that InputInt is still static.

[hey]

Quote:

Originally Posted by staykovmarin

Post your current code (also a partial exception is really of no help).

I have a feeling that InputInt is still static.

import java.util.Scanner;

class Input {
public int InputInt() {
int x = 0;
Scanner in = new Scanner(System.in);

// reads int from the console
// and stores into x
x = in.nextInt();

// notice that now you can close the stream, since the method is non static
in.close();

return x;
}

}
___________________

import java.util.Scanner;

class Input {
public int InputInt() {
int x = 0;
Scanner in = new Scanner(System.in);

// reads int from the console
// and stores into x
x = in.nextInt();

// notice that now you can close the stream, since the method is non static
in.close();

return x;
}

}



PS: how do you separate code from a message?

[staykovmarin]

Post your Min class too?

Use the code tags: [ code][/ code]

[hey]

Code:

import java.util.Scanner;

class Min {
	public static void main(String[] args) {
		int x = 0, y = 0, z = 0, f = 0, i = 0;
		Input input = new Input();
		
		x = input.InputInt();
		System.out.println(x);
		y = input.InputInt();
		System.out.println(y);
		
	}
}

[staykovmarin]

Code:

import java.util.Scanner;

class Min {
	public static void main(String[] args) {
		int x = 0, y = 0, z = 0, f = 0, i = 0;
		Input input = new Input();
		
		x = input.InputInt();
		System.out.println(x);
		y = input.InputInt();
		System.out.println(y);
		
		input.close();
	}
}

class Input {
	Scanner in;
	public int InputInt() {
		int x = 0;
		in = new Scanner(System.in);

		// reads int from the console
		// and stores into x
		x = in.nextInt();
		return x;
	}

	public void close() {
		in.close();
	}
}

So after a little bit of reading, i found out that after you close a stream, it cant be reopened, even if you create a new one (although i swear that it worked fine when i did it :\ ) So here is another solution. Just close the stream after you are done getting the numbers.

[hey]

Quote:

Originally Posted by staykovmarin

Code:

import java.util.Scanner;

class Min {
	public static void main(String[] args) {
		int x = 0, y = 0, z = 0, f = 0, i = 0;
		Input input = new Input();
		
		x = input.InputInt();
		System.out.println(x);
		y = input.InputInt();
		System.out.println(y);
		
		input.close();
	}
}

class Input {
	Scanner in;
	public int InputInt() {
		int x = 0;
		in = new Scanner(System.in);

		// reads int from the console
		// and stores into x
		x = in.nextInt();
		return x;
	}

	public void close() {
		in.close();
	}
}

So after a little bit of reading, i found out that after you close a stream, it cant be reopened, even if you create a new one (although i swear that it worked fine when i did it :\ ) So here is another solution. Just close the stream after you are done getting the numbers.

But in this case, I cannot use that package Input as an independable.. i mean, I have to close the thread from the main program .. is that correct?
thnx