Using java fix the code I implemented so that it passes the JUnit Tests. MATRIX3 public...
Using java fix the code I implemented so that it passes the JUnit Tests.
MATRIX3
public class Matrix3 {
private double[][] matrix;
/**
* Creates a 3x3 matrix from an 2D array
* @param v array containing 3 components of the desired vector
*/
public Matrix3(double[][] array) {
this.matrix = array;
}
/**
* Clones an existing matrix
* @param old an existing Matrix3 object
*/
public Matrix3(Matrix3 old) {
matrix = new double[old.matrix.length][];
for(int i = 0; i < matrix.length; i++) {
matrix[i] = new double[old.matrix[i].length];
for(int j = 0; j < matrix[i].length; j++) {
matrix[i][j] = old.matrix[i][j];
}
}
}
/**
* Returns a matrix element at a row, column
* @param row row
* @param column column
* @return matrix element as a scalar
*/
public double getElement (int row, int column){
return matrix[row][column];
}
/**
* Returns matrix elements as a 2D array
* @return 2D array containing matrix elements
*/
public double[][] getElements (){
return matrix;
}
VECTOR3
public class Vector3 implements Comparable <Vector3>{
private final double x;
private final double y;
private final double z;
/**
* Creates a 3D vector from an array
* @param v array containing 3 components of the desired vector
*/
public Vector3(double[] v) {
this(v[0], v[1], v[2]);
}
/**
* Creates a 3D vector from 3 numeric scalar components
* @param x x coordinate
* @param y y coordinate
* @param z z coordinate
*/
public Vector3(double x, double y, double z) {
this.x = x;
this.y = y;
this.z = z;
}
/**
* Clones an existing vector
* @param old an existing Vector3 object
*/
public Vector3(Vector3 old) {
this(old.x, old.y, old.z);
}
/**
* Returns a vector component at a specified index
* @param index the index of the vector component
* @return vector component as a scalar
*/
public double getElement (int index){
return new double[] {x, y, z}[index];
}
/**
* Returns vector components as an array
* @return
*/
public double[] getElements (){
return new double[] {x, y, z};
}
MVMATH
public class MVMath {
/**
* Multiplies a matrix by a vector
* @param m matrix
* @param v vector
* @return new matrix object containing the result
*/
public static Vector3 multiply (Matrix3 m, Vector3 v){
}
/**
* @param m1 matrix 1
* @param m2 matrix 2
* @return new matrix object containing the result
*/
public static Matrix3 multiply(Matrix3 m1, Matrix3 m2) {
double arr[][] = new double[3][3];
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 3; j++) {
double sum = 0;
for (int k = 0; k < 3; k++)
sum += m1.getElement(i, k) * m2.getElement(k, j);
arr[i][j] = sum;
}
}
return new Matrix3(arr);
}
/**
* Computes a cross product of two vectors
* @param v1 vector 1
* @param v2 vector 2
* @return a new vector object containing the result
*/
public static Vector3 crossProduct (Vector3 v1, Vector3 v2){
double x, y, z;
x = v1.getElement(1) * v2.getElement(2) - v1.getElement(2) * v2.getElement(1);
y = v1.getElement(2) * v2.getElement(0) - v1.getElement(0) * v2.getElement(2);
z = v1.getElement(0) * v2.getElement(1) - v1.getElement(1) * v2.getElement(0);
return new Vector3(x, y, z);
}
/**
* Computes a dot product of two vectors
* @param v1 vector 1
* @param v2 vector 2
* @return dot product (a scalar)
*/
public static double dotProduct (Vector3 v1, Vector3 v2){
return v1.getElement(0)*v2.getElement(0)+v1.getElement(1)*v2.getElement(1)+v1.getElement(2)*v2.getElement(2);
}
}
JUnit:
public class MVMathTest {
@Test
public void testMatrixMult() {
double[][] one = {{1d, 2d, 3d},
{4d, 5d, 6d},
{7d, 8d, 9d}};
double[][] two = {{11d, 12d},
{21d, 22d},
{31d, 32d}};
double[][] expected = {{146d, 152d},
{335d, 350d},
{524d, 548d}};
Matrix3 m1= new Matrix3 (one);
Matrix3 m2= new Matrix3 (two);
double [][] result = MVMath.multiply(m1, m2).getElements();
String error = String.format("Matrix multiplication failed ");
for (int i = 0; i < expected.length; i++){
for (int j = 0; j < expected[0].length; j++){
assertEquals(error, result[i][j], expected[i][j], 1e-6);
}
}
}
@Test
public void testMatrixMult2() {
double[][] one = {{1d, 2d, 3d},
{4d, 5d, 6d}};
Matrix3 m1= new Matrix3 (one);
try {
MVMath.multiply(m1, m1);
String error = String.format("MVMath.multiply() failed to throw an exception");
fail(error);
} catch (IllegalArgumentException x) {
// ok
} catch (Exception x) {
fail("wrong type of exception thrown");
}
}
}
Homework Answers
Here is the completed code for this problem. Please note that I have completed the code for passing the given JUnit tests only (for the multiply method), if there are more tests that I’m not aware of, I can’t help with that. I have also completed multiply method taking Matrix3 and Vector3 objects. Comments are included, go through it, learn how things work and let me know if you have any doubts or if you need anything to change. If you are satisfied with the solution, please rate the answer. If not, PLEASE let me know before you rate, I’ll help you fix whatever issues. Thanks
Note: Your Vector3 class need to implement compareTo method to compile correctly. If you do not want that, please remove ‘implements Comparable<Vector3>’ from Vector3 class header before compiling.
// MVMath.java
public class MVMath {
/**
*
* Multiplies a matrix by a vector
*
* @param m
* matrix
*
* @param v
* vector
*
* @return new matrix object containing the result
*/
public static Vector3 multiply(Matrix3 m, Vector3 v) {
if (m.getElements()[0].length != v.getElements().length) {
// number of columns in m must be equal to number of elements in v,
// otherwise we can't perform multiplication
throw new IllegalArgumentException();
}
double arr[] = new double[v.getElements().length];
for (int i = 0; i < arr.length; i++) {
double sum = 0;
// multiplying every j'th element in row i in matrix with j'th
// element in vector, summing values
for (int j = 0; j < m.getElements()[0].length; j++) {
sum += m.getElement(i, j) * v.getElement(j);
}
//storing sum in arr[i]
arr[i] = sum;
}
return new Vector3(arr);
}
/**
*
* @param m1
* matrix 1
*
* @param m2
* matrix 2
*
* @return new matrix object containing the result
*/
public static Matrix3 multiply(Matrix3 m1, Matrix3 m2) {
// finding rows and columns in m1
int row1 = m1.getElements().length;
int col1 = m1.getElements()[0].length;
// finding rows and columns in m2
int row2 = m2.getElements().length;
int col2 = m2.getElements()[0].length;
// if num columns in first matrix is not equal to num rows in second,
// matrices cant be multiplied.
if (col1 != row2) {
// throwing exception
throw new IllegalArgumentException();
}
double arr[][] = new double[row1][col2];
for (int i = 0; i < row1; i++) {
for (int j = 0; j < col2; j++) {
double sum = 0;
for (int k = 0; k < col1; k++)
sum += m1.getElement(i, k) * m2.getElement(k, j);
arr[i][j] = sum;
}
}
return new Matrix3(arr);
}
/**
*
* Computes a cross product of two vectors
*
* @param v1
* vector 1
*
* @param v2
* vector 2
*
* @return a new vector object containing the result
*/
public static Vector3 crossProduct(Vector3 v1, Vector3 v2) {
double x, y, z;
x = v1.getElement(1) * v2.getElement(2) - v1.getElement(2)
* v2.getElement(1);
y = v1.getElement(2) * v2.getElement(0) - v1.getElement(0)
* v2.getElement(2);
z = v1.getElement(0) * v2.getElement(1) - v1.getElement(1)
* v2.getElement(0);
return new Vector3(x, y, z);
}
/**
*
* Computes a dot product of two vectors
*
* @param v1
* vector 1
*
* @param v2
* vector 2
*
* @return dot product (a scalar)
*/
public static double dotProduct(Vector3 v1, Vector3 v2) {
return v1.getElement(0) * v2.getElement(0) + v1.getElement(1)
* v2.getElement(1) + v1.getElement(2) * v2.getElement(2);
}
}
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Using java fix the code I implemented so that it passes the
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