7 – Methods Answers

1) Write a method that accepts the length and width of a rectangle and returns the perimeter of the rectangle

double Perimeter(double length, double width)
{
    return length*2 + width*2;
}

2) Write a method that accepts the base and height of a triangle and returns the area of the triangle

double areaTriangle(double base, double height)
{
   return 0.5*base*height;
}

3) Write a method that accepts three integers as paramaters and returns the average of the integers.

double average(int a, int b, int c)
{
    return((a+b+c)/3.0);
}

4) Write a method that accepts an integer array as a parameter and returns the average of the values of that array.

double average(int [] numbers)
{
    double av = 0;
    double total = 0;
    for(int n: numbers)
    {
    total += n;
    }
    return total/numbers.length;
}

5) Write a method that accepts an integer array as a parameter and returns the minium value in that array

double min(int [] numbers)
{
    int minVal = numbers[0];
    for (int n : numbers)
    {
    if (n < minVal) minVal = n;
    }
    return minVal;
}

or

double min(int [] numbers)
{
    Arrays.sort(numbers);
    return numbers[0];
}

6) Write a method that returns the hypotenuse of a triangle when the other two sides are int a and int b. (Remember: hypotenuse squared equals a squared plus b squared)

double hypotenuse(double a, double b)
{
    return Math.sqrt(a*a + b*b);
}

7) The scalar product of u=(u1,u2,u3) and v=(v1,v2,v3) is defined to be u1v1+u2v2+u3v3. Write a method that accepts two int arrays as parameters and returns an int representing the scalar product of those two arrays

double scalarProduct(int [] u, int [] v) throws Exception
{
    if (u.length != v.length) throw new Exception();
    double product = 0;
    for(int i = 0; i<u.length; i++)
    {
    product += u[i]*v[i];
    }
    return product;
}

8) If A = (a1,a2, …an) and B = (b1,b2, …bn) then the vector sum of the two arrays A + B = (a1+b1, a2+b2, … , an+bn). Write a method that accepts two arrays as parameters and returns an array representing the vector sum of those two arrays.

double [] vectorSum(int [] u, int [] v) throws Exception
{
    if (u.length != v.length) throw new Exception();
    double [] sum = new double[u.length];
    for(int i = 0; i<u.length; i++)
    {
    sum[i] = u[i] + v[i];
    }
    return sum;
}

9) The Euclidean distance between two points A = (a1,a2, …an) and B = (b1,b2, …bn) is defined as sqrt((a1-b1)² + (a2-b2)² +… + (an-bn)²). Write a method that accepts two int arrays representing A and B as parameters and returns a double representing the Euclidean distance between them.

double [] eDistance(int [] u, int [] v) throws Exception
{
  if (u.length != v.length) throw new Exception();
  double [] sum = new double[u.length];
  double dist = 0;
  for(int i = 0; i<u.length; i++)
  {
       dist += Math.pow((u[i]-v[i]),2);
  }
  return sum;
}