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Thread: Square root not working

  1. #1
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    Default Square root not working

    This is my program that does the distance formula for you. I don't understand why it can't find the method for doing square root unless that changed? My code is here and the error is below it.

    import java.lang.Math;
     
    public class Distance_Formula {
     
    	public static void main(String [] args) {
     
    		userInput input = new userInput();
    		double x1 = 0.0;
    		double x2 = 0.0;
    		double y1 = 0.0;
    		double y2 = 0.0;
    		double distancePreSquareRoot = 0.0;
    		double distancePostSquareRoot = 0.0;
    		String x1prompt = "Enter the X1 value: ";
    		String x2prompt = "Enter the X2 value: ";
    		String y1prompt = "Enter the Y1 value: ";
    		String y2prompt = "Enter the Y2 value: ";
     
    		input.getUserInput(x1prompt);
    		x1 = Double.parseDouble(input.input);
    		input.getUserInput(x2prompt);
    		x2 = Double.parseDouble(input.input);
    		input.getUserInput(y1prompt);
    		y1 = Double.parseDouble(input.input);
    		input.getUserInput(y2prompt);
    		y2 = Double.parseDouble(input.input);
     
    		distancePreSquareRoot = (((x2 - x1) * (x2 - x1)) + ((y2 - y1) * (y2 - y1)));
     
    		distancePostSquareRoot = sqrt(distancePreSquareRoot);
     
    		System.out.println("The distance between (" + x1 + "," + y1 + " and (" + x2 + "," + y2 + ") is: " + distancePostSquareRoot);
     
     
    	}
     
    }

    Error:

    Distance_Formula.java:30: cannot find symbol
    symbol  : method sqrt(double)
    location: class Distance_Formula
                    distancePostSquareRoot = sqrt(distancePreSquareRoot);
                                             ^
    1 error
    Press any key to continue . . .
    Last edited by sp11k3t3ht3rd; January 7th, 2011 at 06:14 PM.


  2. #2
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    Default Re: Square root not working

    I figured it out. I needed you put Math.sqrt. Sorry about that!

  3. #3
    Super Moderator helloworld922's Avatar
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    Default Re: Square root not working

    In Java there's no such thing as a "global" variable/method. Thus, for methods outside of your current class (including the inheritance hierarchy) you must quantify where that variable/method came from.

    distancePostSquareRoot = Math.sqrt(distancePreSquareRoot); // sqrt is found inside the Math class as a static method

    An alternative available starting in SE 5 is something known as "static imports". This lets you do things such as importing static methods/variables and using them without needing to quantify where they come from. Note that you should be careful when using static imports.

    import static java.lang.Math.sqrt;
     
    public class SomeClass
    {
        public static void main(String[] args)
        {
            double a = sqrt(5);
        }
    }

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