Java：带数组的算术（乘法，加法，减法）

Question

Below is a method I want to use to do calculations and return a value. The equation is: L = T + R*p - b where L, R, p, and b will have a subscript (0-5). R is a 3x3 matrix, which is stored/generated in another class, p and b are arrays of 6 sets of (x,y,z) coordinates. L should have 6 total values when the program runs, and I have chosen to store them in an array.

The first error I got was when I didn't have rotationMultiply or the for loops. Instead I had rotation*platformCoords . So now that I have gotten rid of that error, I get a new error "Syntax error on token "*", invalid AssignmentOperator" for the line rotation[i][j]*platformCoords[i] and another error, The operator - is undefined for the argument type(s) double, double[], for line tLength + rotationMultiply - baseCoords; .

I'm sure there will be more errors once I get those taken care of, so if you can anticipate any and give me a heads up on where I can do some more learning I'd appreciate it.

This is one piece of a program I'm attempting to write that will help control a stewart platform.

public class LiCalc {

double length[];

public double legLength(double tLength, double[][] rotation, double[] platformCoords, double[] baseCoords ){

    double rotationMultiply;

      for (int i = 0; i < 3; i++){
          for (int j = 0; j < 3; j++){
              rotation[i][j]*platformCoords[i];
              return rotationMultiply;
          }
      }    

    length = tLength + rotationMultiply - baseCoords;

    return length[];

}

}

Answer 1

This answer is by no means mathematically 100% correct. I just corrected all obvious flaws and compiletime errors.

Try the following code and build the correct answer on it:

import java.util.Arrays;

public final class LiCalc
{

    private LiCalc()
    {

    }

    public static double[] legLength(double tLength[], double[][] rotation, double[] platformCoords, double[] baseCoords)
    {

        double[] rotatedCoords = new double[platformCoords.length];

        for (int i = 0; i < 3; i++)
        {
            double rotatedValue = 0;
            for (int j = 0; j < 3; j++)
            {
                rotatedValue += rotation[i][j] * platformCoords[i];
            }
            rotatedCoords[i] = rotatedValue;
        }

        double[] length = new double[platformCoords.length];

        for (int i = 0; i < 3; i++)
        {
            length[i] = tLength[i] + rotatedCoords[i] - baseCoords[i];
        }

        return length;

    }

    public static void main(String[] args)
    {
        System.out.println(Arrays.toString(LiCalc.legLength(new double[]{1, 0, 0},
                new double[][] { { 1, 0, 0 }, { 0, 1, 0 }, { 0, 0, 1 } }, new double[] { 0, 1, 1 }, new double[] { 1,
                        0, 0 })));
    }
}