## Version 3

```public class QuadraticEquation {
// a quadratic equation a*x^2 + b*x + c = 0

double a;
double b;
double c;

QuadraticEquation(double a1, double b1, double c1) {
// create a new quadratic equation with the given coefficients
a = a1;
b = b1;
c = c1;
}

private String toSignedString(double d) {
// creates string with sign from double value
if (d >= 0) {
return("+ " + Double.toString(d));
}
else {
return("- " + Double.toString(-d));
}
}

private double discriminant() {
// the discriminant of the equation
return(b*b/(4*a*a) - c/a);
}

double[] getSolution() {
// returns vector of solution values
double a1 = -b/(2*a);
double d = discriminant();
double[] result;

if (d > 0) {
result = new double[2];
double dRoot = Math.sqrt(d);
result[0] = a1 + dRoot;
result[1] = a1 - dRoot;
}
else if (d == 0) {
result = new double[1];
result[0] = a1;
}
else {
// d<0: result is empty
result = new double[0];
}

return(result);
}

void print() {
// print the equation to the screen
System.out.println(a + "*x^2 "+ toSignedString(b) + "*x "
+ toSignedString(c));
}
}
```

```public class TestQuadraticEquation {
// simple test program for QuadraticEquation

public static void main (String[] args) {
// get the coefficients from the command line
double a = Double.parseDouble(args[0]);
double b = Double.parseDouble(args[1]);
double c = Double.parseDouble(args[2]);

qe1.print();

double[] result = qe1.getSolution();
int      count =  result.length;
System.out.println("has " + count + " solutions");

if (count > 0) {
System.out.println(result[0]);
}
if (count > 1) {
System.out.println(result[1]);
}
}
}
```

Peter Junglas 8.3.2000