Can't find symbol

[kkid]

I am writing a basic program to find the roots of a quadratic equation using the quadratic formula. However, I am getting the error in the title 11 times, can somebody please explain why?

class Quadratic {


	public static void main(String[] args) {
	calculation(1, 1, -6);
	System.out.println("The quadritic equation entered was:");
	System.out.print(aValue + "x" + "\u00B2");
	System.out.print(" + ");
	System.out.print(bValue + "x");
	System.out.print(" + ");
	System.out.println(cValue);

	System.out.println("The roots are:");
	System.out.println(plusAnswer + " and " + minusAnswer);
	}


		public static void calculation(int a, int b, int c) {
		aValue = a;
		bValue = b;
		cValue = c;

		if (aValue <= 0) {
		System.out.println("Only enter a positive number for a");
		return;
		}

		else {
		double plusAnswer = ((b*(-1))+sqrt(pow(b,2)-(4*a*c)))/(2*a);
		double minusAnswer = ((b*(-1))-(sqrt(pow(b,2)-(4*a*c))))/(2*a);
		}

		}


}

[kkid]

Sorted 4 of the errors, forgot the "int" before aValue...

        public static void calculation(int a, int b, int c) {
        int aValue = a;
        int bValue = b;
        int cValue = c;

[kkid]

I still have 7 of the errors though

[Norm]

Please post the full text of the error messages that show the lines where the errors are happening.

[PhQ]

There are no variables called aValue, bValue, cValue, plusAnswer and minusAnswer in your main method.
Also there is no method called pow() and sqrt() in your class. I am guessing you are trying to use the Math class for those methods.

[kkid]

There are no variables called aValue, bValue, cValue, plusAnswer and minusAnswer in your main method.
Also there is no method called pow() and sqrt() in your class. I am guessing you are trying to use the Math class for those methods.

do all variables have to be stated in the main method then?
can't I state them in the calculation method?


I have int before the aValue, bValue and cValue though, isn't that declaring them (and double before the "answer" variables)



Do I need Math.*** for the calc methods then?

[kkid]

There are more errors now, it can't find the variables...

class Quadratic {


	public static void main(String[] args) {
	int aValue, bValue, cValue;
	double plusAnswer, minusAnswer;
	calculation(1, 1, -6);
	System.out.println("The quadritic equation entered was:");
	System.out.print(aValue + "x" + "\u00B2");
	System.out.print(" + ");
	System.out.print(bValue + "x");
	System.out.print(" + ");
	System.out.println(cValue);

	System.out.println("The roots are:");
	System.out.println(plusAnswer + " and " + minusAnswer);
	}


		public static void calculation(int a, int b, int c) {
		aValue = a;
		bValue = b;
		cValue = c;

		if (aValue <= 0) {
		System.out.println("Only enter a positive number for a");
		return;
		}

		else {
		plusAnswer = ((b*(-1))+Math.sqrt(Math.pow(b,2)-(4*a*c)))/(2*a);
		minusAnswer = ((b*(-1))-(Math.sqrt(Math.pow(b,2)-(4*a*c))))/(2*a);
		}

		}


}

[Norm]

You need to define the variables where they are needed. Some are needed in several methods and those should be defined at the class level. Some are only used in a single method, those should be defined in the method and not in the class.

To call a class's static methods, code the name of the class dot methodname: Math.round()

There are more errors

Please copy and paste here the full text of the error messages.

[kkid]

C:\Users\Mike\Desktop\Learning Java\Programs>javac QuadraticSolver.java
QuadraticSolver.java:21: error: cannot find symbol
aValue = a;
^
symbol: variable aValue
location: class Quadratic
QuadraticSolver.java:22: error: cannot find symbol
bValue = b;
^
symbol: variable bValue
location: class Quadratic
QuadraticSolver.java:23: error: cannot find symbol
cValue = c;
^
symbol: variable cValue
location: class Quadratic
QuadraticSolver.java:25: error: cannot find symbol
if (aValue <= 0) {
^
symbol: variable aValue
location: class Quadratic
QuadraticSolver.java:31: error: cannot find symbol
plusAnswer = ((b*(-1))+Math.sqrt(Math.pow(b,2)-(4*a*c)))/(2*a);
^
symbol: variable plusAnswer
location: class Quadratic
QuadraticSolver.java:32: error: cannot find symbol
minusAnswer = ((b*(-1))-(Math.sqrt(Math.pow(b,2)-(4*a*c))))/(2*a);
^
symbol: variable minusAnswer
location: class Quadratic
6 errors

[kkid]

You need to define the variables where they are needed. Some are needed in several methods and those should be defined at the class level. Some are only used in a single method, those should be defined in the method and not in the class.

I use them two sets of variables in both methods, therefore I need to quote them at a class level?

How do I do this?
I have never done this before

[kkid]

I tried this, it didn't work...

class Quadratic {

int aValue, bValue, cValue;
double plusAnswer, minusAnswer;

	public static void main(String[] args) {
	calculation(1, 1, -6);
	System.out.println("The quadritic equation entered was:");
	System.out.print(aValue + "x" + "\u00B2");
	System.out.print(" + ");
	System.out.print(bValue + "x");
	System.out.print(" + ");
	System.out.println(cValue);

	System.out.println("The roots are:");
	System.out.println(plusAnswer + " and " + minusAnswer);
	}


		public static void calculation(int a, int b, int c) {
		aValue = a;
		bValue = b;
		cValue = c;

		if (aValue <= 0) {
		System.out.println("Only enter a positive number for a");
		return;
		}

		else {
		plusAnswer = ((b*(-1))+Math.sqrt(Math.pow(b,2)-(4*a*c)))/(2*a);
		minusAnswer = ((b*(-1))-(Math.sqrt(Math.pow(b,2)-(4*a*c))))/(2*a);
		}

		}


}

[kkid]

did I do the Math.*** bit right?

[kkid]

I get this with my (bad) adjustment:

C:\Users\Mike\Desktop\Learning Java\Programs>javac QuadraticSolver.java
QuadraticSolver.java:9: error: non-static variable aValue cannot be referenced from a static context
System.out.print(aValue + "x" + "\u00B2");
^
QuadraticSolver.java:11: error: non-static variable bValue cannot be referenced from a static context
System.out.print(bValue + "x");
^
QuadraticSolver.java:13: error: non-static variable cValue cannot be referenced from a static context
System.out.println(cValue);
^
QuadraticSolver.java:16: error: non-static variable plusAnswer cannot be referenced from a static context
System.out.println(plusAnswer + " and " + minusAnswer);
^
QuadraticSolver.java:16: error: non-static variable minusAnswer cannot be referenced from a static context
System.out.println(plusAnswer + " and " + minusAnswer);
^
QuadraticSolver.java:21: error: non-static variable aValue cannot be referenced from a static context
aValue = a;
^
QuadraticSolver.java:22: error: non-static variable bValue cannot be referenced from a static context
bValue = b;
^
QuadraticSolver.java:23: error: non-static variable cValue cannot be referenced from a static context
cValue = c;
^
QuadraticSolver.java:25: error: non-static variable aValue cannot be referenced from a static context
if (aValue <= 0) {
^
QuadraticSolver.java:31: error: non-static variable plusAnswer cannot be referenced from a static context
plusAnswer = ((b*(-1))+Math.sqrt(Math.pow(b,2)-(4*a*c)))/(2*a);
^
QuadraticSolver.java:32: error: non-static variable minusAnswer cannot be referenced from a static context
minusAnswer = ((b*(-1))-(Math.sqrt(Math.pow(b,2)-(4*a*c))))/(2*a);
^
11 errors

[Norm]

Where are the variables: aValue etc defined?

Why do you need them? You can use a,b,c directly in the method. You are using a,b,c here:
plusAnswer = ((b*(-1))+Math.sqrt(Math.pow(b,2)-(4*a*c)))/(2*a);

it didn't work...

What did not work?
You need to post the full text of the error messages.


EDIT: I think we posted at the same time. You should try to put it all in one post and not continue to make changes and new posts.

[PhQ]

I get this with my (bad) adjustment:

C:\Users\Mike\Desktop\Learning Java\Programs>javac QuadraticSolver.java
QuadraticSolver.java:9: error: non-static variable aValue cannot be referenced from a static context
System.out.print(aValue + "x" + "\u00B2");
^
QuadraticSolver.java:11: error: non-static variable bValue cannot be referenced from a static context
System.out.print(bValue + "x");
^
QuadraticSolver.java:13: error: non-static variable cValue cannot be referenced from a static context
System.out.println(cValue);
^
QuadraticSolver.java:16: error: non-static variable plusAnswer cannot be referenced from a static context
System.out.println(plusAnswer + " and " + minusAnswer);
^
QuadraticSolver.java:16: error: non-static variable minusAnswer cannot be referenced from a static context
System.out.println(plusAnswer + " and " + minusAnswer);
^
QuadraticSolver.java:21: error: non-static variable aValue cannot be referenced from a static context
aValue = a;
^
QuadraticSolver.java:22: error: non-static variable bValue cannot be referenced from a static context
bValue = b;
^
QuadraticSolver.java:23: error: non-static variable cValue cannot be referenced from a static context
cValue = c;
^
QuadraticSolver.java:25: error: non-static variable aValue cannot be referenced from a static context
if (aValue <= 0) {
^
QuadraticSolver.java:31: error: non-static variable plusAnswer cannot be referenced from a static context
plusAnswer = ((b*(-1))+Math.sqrt(Math.pow(b,2)-(4*a*c)))/(2*a);
^
QuadraticSolver.java:32: error: non-static variable minusAnswer cannot be referenced from a static context
minusAnswer = ((b*(-1))-(Math.sqrt(Math.pow(b,2)-(4*a*c))))/(2*a);
^
11 errors

You need to make the variables above the main method static.

[kkid]

Where are the variables: aValue etc defined?

Why do you need them? You can use a,b,c directly in the method. You are using a,b,c here:
plusAnswer = ((b*(-1))+Math.sqrt(Math.pow(b,2)-(4*a*c)))/(2*a);

What did not work?
You need to post the full text of the error messages.


EDIT: I think we posted at the same time. You should try to put it all in one post and not continue to make changes and new posts.

Because a, b and c are just parameters of the calculation method and therefore I cannot have their values appear in main (I don't think - I'm new to this).


How do I make them static, do I just type static before them? (I am self-teaching and haven't came across this yet).
What does it mean if they're static?

[kkid]

UPDATE:

I tried putting "static" behind both of the variable declaration and I got no errors when compiling, I'm going to test it out now!


Thank you!

[kkid]

This is my working code:

class Quadratic {

static int aValue, bValue, cValue;
static double plusAnswer, minusAnswer;

	public static void main(String[] args) {
	calculation(1, 1, -6);
	System.out.println("The quadritic equation entered was:");
	System.out.print(aValue + "x" + "\u00B2");
	System.out.print(" + ");
	System.out.print(bValue + "x");
	System.out.print(" + ");
	System.out.println(cValue);

	System.out.println("The roots are:");
	System.out.println(plusAnswer + " and " + minusAnswer);
	}


		public static void calculation(int a, int b, int c) {
		aValue = a;
		bValue = b;
		cValue = c;

		if (aValue <= 0) {
		System.out.println("Only enter a positive number for a");
		return;
		}

		else {
		plusAnswer = ((b*(-1))+Math.sqrt(Math.pow(b,2)-(4*a*c)))/(2*a);
		minusAnswer = ((b*(-1))-(Math.sqrt(Math.pow(b,2)-(4*a*c))))/(2*a);
		}

		}


}

How do I print a ² symbol though?
I searched online and it said to type \u00B2 but it just comes up with a filled in rectangle.

[JosAH]

Why should 'a' be positive?

kind regards,

Jo

[kkid]

Why should 'a' be positive?

Thanks for pointing this out, I just didn't think it through much, I meant for it to be not zero, I'll change this now.

How do I print a ² symbol though?
I searched online and it said to type \u00B2 but it just comes up with a filled in rectangle.