Java problem

whats newxt

//So i'm just learning java myself for the last few days and i have a basic program:

import java.util.Scanner;

public class test1 {
public static void main(String args[]){
int a = 10;
int b = 20;

Scanner v1 = new Scanner(System.in);
System.out.println("Number for a is: " + a + v1.nextLine());

Scanner v2 = new Scanner(System.in);
System.out.println("Number for b is: " + b + v2.nextLine());

System.out.println(a);
System.out.println(b);

}
}

//the program works but not as i intended it to, i want to have two integers a and b and i want to take user input (Scanner) and add the user input to the integer store it and print the stored value of a and b at the end. What am i doing wrong. Thanks for your help

Maximus Alexander

Both integers a and b are set to 0, you're printing those zero values along with the any input from the scanner. You never actually assign values to a or b.

Change

System.out.println("Number for a is: " + a + v1.nextLine());

to

a = v1.nextInt();
System.out.println("Number for a is: " + a);

whats newxt

Maximus Alexander wrote: »

Both integers a and b are set to 0, you're printing those zero values along with the any input from the scanner. You never actually assign values to a or b.

Change

System.out.println("Number for a is: " + a + v1.nextLine());

to

a = v1.nextInt();
System.out.println("Number for a is: " + a);

Thanks it worked:

import java.util.Scanner;

public class test1 {
	public static void main(String args[]){
		int a = 10;
		int b = 20;
		
		Scanner v1 = new Scanner(System.in);
		a = a + v1.nextInt();
		System.out.println("Number for a is: " + a);
		
		Scanner v2 = new Scanner(System.in);
		b = b + v1.nextInt();
		System.out.println("Number for b is: " + b);
		
		System.out.println("The stored value foa a is: " + a);
		System.out.println("The stored value for b is: " + b);

	}
}

[/QUOTE]

Maximus Alexander

whats newxt wrote: »

Thanks it worked:

import java.util.Scanner;

public class test1 {
	public static void main(String args[]){
		int a = 10;
		int b = 20;
		
		Scanner v1 = new Scanner(System.in);
		a = a + v1.nextInt();
		System.out.println("Number for a is: " + a);
		
		Scanner v2 = new Scanner(System.in);
		b = b + v1.nextInt();
		System.out.println("Number for b is: " + b);
		
		System.out.println("The stored value foa a is: " + a);
		System.out.println("The stored value for b is: " + b);

	}
}

The important thing is though, do you understand why it worked? Because I just noticed that I misread your original intention.

whats newxt

I'm not to sure i think it's because when you use .nextLine it thinks you're working with a string and when your use .nextInt it knows you're working with integers?

Maximus Alexander

Yes that's true, and more specifically, the + operator has two functions. On numeric types it performs addition, on Strings it performs concatenation.

Because you originally had your addition (a + the value of nextLine()) as a parameter to the System.out.println() function, which takes a String, it just concatenated the string representation of a with whatever came in via the scanner. This would still have happened if you had used nextInt().

For example if:

a = 10
v1.nextInt() = 10

You'd have gotten 1010.

whats newxt

Maximus Alexander wrote: »

Yes that's true, and more specifically, the + operator has two functions. On numeric types it performs addition, on Strings it performs concatenation.

Because you originally had your addition (a + the value of nextLine()) as a parameter to the System.out.println() function, which takes a String, it just concatenated the string representation of a with whatever came in via the scanner. This would still have happened if you had used nextInt().

For example if:

a = 10
v1.nextInt() = 10

You'd have gotten 1010.

Thanks i see what was happening now, can you recommend any books for learning java most the tutorials on you tube skip over important parts.

Maximus Alexander

I got the older 8th edition of this a few years ago and I would highly recommend it. Starts with the basics and works up, covers a lot of ground. It's a big book but it's quite comprehensive and covers the details well. It also has plenty of exercises.