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Thread: Why does java not honor my if/else statments

  1. #1
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    Default Why does java not honor my if/else statments

    Hey everyone, complete noob here, I'm writing a program for my class about a quadratic equation. Everything in the code seems correct, only java just doesnt seem to care about if/else statements, anyway here is my code:
    /**
     * 
     */
    package edu.vtc.aav10260.cis2261;
    import java.util.Scanner;
    /**
     * @author andre
     *
     */
    public class Quadratic {
     
    	/**
    	 * @param args unused
    	 */
    	public static void main(String[] args) {
    		Scanner input = new Scanner(System.in);
    		String equation = "( ax^2 + bx + c = 0)"; 
    		System.out.println(equation);
    		System.out.println("Enter the coefficients");
    		System.out.print("a= "); 
    		double a = input.nextDouble();
    		System.out.print("b= ");
    		double b = input.nextDouble();
    		System.out.print("c= ");
    		double c = input.nextDouble();
    		System.out.println();
    		double determinant = Math.sqrt((b*b)-(4*a*c));
    		System.out.println(determinant);
     
    		if (determinant < 0)
    		{
    		System.out.println("There are no solutions");
    		} 
    		else if  (determinant == 0)
    		{
    		System.out.println("There is one solution");
    		double solution = (-b/(2*a));
    		System.out.println(solution);
    		}
    		else if (determinant > 0);
    		{
    		System.out.println("There are two solutions");
    		double solution1 = ((-b + determinant)/(2*a));
    		double solution2 = ((-b - determinant)/(2*a));
    		System.out.println(solution1);
    		System.out.println(solution2);
    		}
     
     
    	}
     
    }
    The program works fine if the determinant is positive and has two solutions, but if it is only one solution, the results read like this:

    ( ax^2 + bx + c = 0)
    Enter the coefficients
    a= 1
    b= 2
    c= 1

    0.0
    There is one solution
    -1.0
    There are two solutions
    -1.0
    -1.0

    And if the determinant is negative, giving no solutions, it looks like this:

    ( ax^2 + bx + c = 0)
    Enter the coefficients
    a= 1
    b= 2
    c= 3

    NaN
    There are two solutions
    NaN
    NaN

    This makes no sense as my statements explicitly state certain things to do if the determinant is less than, equal to or greater than zero, however the program seems to just print everything out regardless of what the determinant is
    Last edited by helloworld922; September 11th, 2012 at 11:38 PM. Reason: please use [code] tags


  2. #2
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    Default Re: Why does java not honor my if/else statments

    Quote Originally Posted by mflb94 View Post
    ... java just doesnt seem to care about if/else statements...
    .
    .
    .
    		else if  (determinant == 0)
    		{
    		    System.out.println("There is one solution"); // <--- This is where things are OK, right?
    		    double solution = (-b/(2*a));
    		    System.out.println(solution);
    		}
    		else if (determinant > 0); //<---This is where things go wrong, right?
    		{
    		    System.out.println("There are two solutions");
    .
    .
    .
    This makes no sense as my statements explicitly state certain things to do if the determinant is less than, equal to or greater than...
    Well, I can certainly see what you intended for it to do.

    However...

    The program does what you tell it to do, not what you intend for it to do. (Does this make me smarter than the "computer" or not?)

    Generic methodology for debugging: When things seem to be going right, but then they go wrong, look very carefully at the place where things go wrong...

    Bottom line: Trust me, Java cares. It really, really cares.


    Cheers!


    Z
    Last edited by Zaphod_b; September 11th, 2012 at 11:48 PM.

  3. #3
    Super Moderator helloworld922's Avatar
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    Default Re: Why does java not honor my if/else statments

    else if (determinant > 0);
    You have an extra semi-colon at the end. This is basically telling Java to ignore this else/if branch.

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