eecenja - 8 months ago 33

Java Question

This question is for my intro to Java class and the question is asking me to use classes to solve a quadratic equation.

I am trying to fix my class so that it doesn't return NaN. I have used

`Math.abs()`

`public class Quadratic`

{

//Private data members

private double a;

private double b;

private double c;

private double posX;

private double negX;

//Deafault constructor

public void Quadratic()

{

a = 1;

b = 0;

c = 0;

posX = 0;

negX = 0;

}

//The mutators

public void setQuad(Double alpha, double bravo, double charlie)

{

alpha = a;

bravo = b;

charlie = c;

getQuad();

}

//The accessors

public double getQuad()

{

double temp = (Math.pow(b, 2) - (4 * a * c));//getting the number inside the root

if(temp < 0)

temp = Math.abs(temp);

//ensures that the function can run until complex numbers are sorted

posX = (-b + (Math.sqrt(temp)))/(2 * a);//calculates when added

negX = (-b + (Math.sqrt(temp)))/(2 * a);//calculates when subtracted

//error: Keep getting NaN for answers, already accounted for negative inside the root

// not a 0 in the descriminant.

return 0;

}

//My toString which is what will be output at System.out.println(N)

public String toString()

{

if(negX == posX)

return "X = "+ negX;

else

return "X = "+ negX +" and "+ posX;

}

}

Is my math incorrect, or am I using the math utilities incorrectly?

Answer

- Your construct was assigning your fields to the local parameters in the constructor
- usually you would want to allow th ability to assign fields from constructor, thus i put one in
- Your negX assignment was the same as posX
- getQuad doesn't need to return anything with your implementation
- Your accesor getQuad wasn't really an accesor, it was more of a mutator changing posX and negX, implemented what accessors would be below

public class Quadratic { private double a; private double b; private double c; private double posX; private double negX;

```
//Default constructor
public Quadratic()
{
//1.
a = 0;
b = 0;
c = 0;
posX = 0;
negX = 0;
}
public Quadratic(double a, double b, double c){
//2.
this.a = a;
this.b = b;
this.c = c;
this.posX = 0;
this.negX = 0;
}
//The mutators
public void setQuad(Double alpha, double bravo, double charlie)
{
a = alpha;
b = bravo;
c = charlie;
getQuad();
}
public void getQuad()
{
//4.
double temp = (Math.pow(b, 2) - (4 * a * c));//getting the number inside the root
if(temp < 0)
temp = Math.abs(temp);
//ensures that the function can run until complex numbers are sorted
posX = (-b + (Math.sqrt(temp)))/(2 * a);
//3.
negX = (-b - (Math.sqrt(temp)))/(2 * a);
}
//Accesors 5.
public double getA(){
return this.a
}
public double getB(){
return this.b
}
public double getC(){
return this.c
}
//Overriding toString
public String toString()
{
if(negX == posX)
return "X = "+ negX;
else
return "X = "+ negX +" and "+ posX;
}
```

}