260 lines
6.9 KiB
Java
260 lines
6.9 KiB
Java
/**
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* Matrix data-type.
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*
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* @author Kyler Smith, 2017
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*/
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public class Matrix {
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public static void main(String[] args) {
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int[][] data1 = new int[0][0];
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int[][] data2 = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
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int[][] data3 = {{1, 4, 7}, {2, 5, 8}, {3, 6, 9}};
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Matrix m1 = new Matrix(data1);
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Matrix m2 = new Matrix(data2);
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Matrix m3 = new Matrix(data3);
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System.out.println("m1 --> Rows: " + m1.getRows() + " Columns: " + m1.getColumns());
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System.out.println("m2 --> Rows: " + m2.getRows() + " Columns: " + m2.getColumns());
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System.out.println("m3 --> Rows: " + m3.getRows() + " Columns: " + m3.getColumns());
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//check for reference issues
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System.out.println("m2 -->\n" + m2);
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data2[1][1] = 101;
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System.out.println("m2 -->\n" + m2);
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//test equals
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System.out.println("m2==null: " + m2.equals(null)); //false
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System.out.println("m3==\"MATRIX\": " + m2.equals("MATRIX")); //false
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System.out.println("m2==m1: " + m2.equals(m1)); //false
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System.out.println("m2==m2: " + m2.equals(m2)); //true
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System.out.println("m2==m3: " + m2.equals(m3)); //false
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//test operations (valid)
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System.out.println("2 * m2:\n" + m2.scale(2));
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System.out.println("m2 / 2:\n" + m2.divide(2));
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System.out.println("m2 + m3:\n" + m2.plus(m3));
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System.out.println("m2 - m3:\n" + m2.minus(m3));
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System.out.println("m2 * m3: \n"+m2.multiply(m3));
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}
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/**
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* Data needs to be a deep copy as not to change the original state.
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*/
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private int[][] data;
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/**
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* Constructor for the matrix takes in a 2D array
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*
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* @param pData
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*/
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public Matrix(int[][] pData) {
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/** Make a deep copy of the data */
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if(pData.length != 0) {
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int[][] newData = new int[pData.length][pData[0].length];
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for(int i = 0; i < pData.length; i++)
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for(int j = 0; j < pData[0].length; j++)
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newData[i][j] = pData[i][j];
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this.data = newData;
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} else {
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this.data = null;
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}
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}
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/**
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* Returns the element specified by the given location
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*
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* @param x : x cooridinate
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* @param y : y cooridinate
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* @return int : value at location
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*/
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public int getElement(int x, int y) {
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return data[x][y];
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}
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/**
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* Returns the number of rows in the Matrix
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*
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* @return rows
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*/
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public int getRows() {
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if(this.data == null)
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return 0;
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return data.length;
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}
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/**
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* Returns the number of rows in the Matrix
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*
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* @return columns
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*/
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public int getColumns() {
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if(this.data == null)
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return 0;
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return data[0].length;
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}
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/**
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* Returns this matrix scaled by a factor. That is, computes sA where s is a
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* constant and A is a matrix (this object).
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*
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* @param scalar : value to scale by
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* @return A new matrix scaled by the scalar value
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*/
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public Matrix scale(int scalar) {
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int[][] newData = new int[this.data.length][this.data[0].length];
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for (int i = 0; i < this.getRows(); ++i)
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for(int j = 0; j < this.getColumns(); ++j)
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newData[i][j] = this.data[i][j] * scalar;
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return new Matrix(newData);
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}
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/**
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* Returns this matrix divided by a factor. That is, computes sA where s is a
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* constant and A is a matrix (this object).
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*
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* @param scalar : value to divide by
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* @return A new matrix scaled by the scalar value
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*/
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public Matrix divide(int scalar) {
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int[][] newData = new int[this.data.length][this.data[0].length];
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for (int i = 0; i < this.getRows(); ++i)
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for(int j = 0; j < this.getColumns(); ++j)
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newData[i][j] = this.data[i][j] / scalar;
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return new Matrix(newData);
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}
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/**
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* Adds this matrix to another matrix.
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*
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* @param other : Matrix to be added
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* @return addend
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*/
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public Matrix plus(Matrix other) throws RuntimeException {
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int[][] newData = new int[this.data.length][this.data[0].length];
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if(this.getRows() != other.getRows() || this.getColumns() != other.getColumns())
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throw new RuntimeException("Not the same size matrix.");
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for (int i = 0; i < this.getRows(); ++i)
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for(int j = 0; j < this.getColumns(); ++j)
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newData[i][j] = this.data[i][j] + other.getElement(i, j);
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return new Matrix(newData);
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}
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/**
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* Subtracts this matrix from another matrix.
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*
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* @param other : Matrix to be subtracted
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* @return difference
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*/
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public Matrix minus(Matrix other) throws RuntimeException {
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int[][] newData = new int[this.data.length][this.data[0].length];
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if(this.getRows() != other.getRows() || this.getColumns() != other.getColumns())
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throw new RuntimeException("Not the same size matrix.");
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for (int i = 0; i < this.getRows(); ++i)
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for(int j = 0; j < this.getColumns(); ++j)
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newData[i][j] = this.data[i][j] - other.getElement(i, j);
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return new Matrix(newData);
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}
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/**
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* Multiplies this matrix with another matrix.
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*
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* @param other : Matrix to be multiplied with
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* @return product
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*/
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public Matrix multiply(Matrix other) throws RuntimeException {
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int[][] newData = new int[this.data.length][other.getColumns()];
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if(this.getColumns() !=other.getRows())
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throw new RuntimeException("The two matrices cannot be multiplied.");
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int sum;
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for (int i = 0; i < this.getRows(); ++i)
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for(int j = 0; j < other.getColumns(); ++j){
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sum = 0;
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for(int k=0;k<this.getColumns();++k){
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sum += this.data[i][k] * other.getElement(k, j);
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}
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newData[i][j] = sum;
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}
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return new Matrix(newData);
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}
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/**
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* Checks if the matrix passed is equal to this matrix
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*
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* @param other : the other matrix
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* @return boolean
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*/
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public boolean equals(Matrix other) {
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return this == other;
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}
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/**
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* Returns the Matrix as a String in the following format
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*
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* [ a b c ] ...
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* [ x y z ] ...
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* [ i j k ] ...
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* ...
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*
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* @return Matrix as String
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* TODO: Work formatting for different digit sizes
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*/
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public String toString() {
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String str = "";
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for(int i = 0; i < this.data.length; i++) {
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str += "[ ";
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for(int j = 0; j < this.data[0].length; j++) {
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str += data[i][j];
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str += " ";
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}
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str += "]";
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str += "\n";
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}
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return str;
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}
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/**
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* Returns transposed matrix of this matrix.
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*
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* @return transposed Matrix.
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*/
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public Matrix transpose() {
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int[][] newData = new int[this.data[0].length][this.data.length];
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for (int i = 0; i < this.getColumns(); ++i)
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for(int j = 0; j < this.getRows(); ++j)
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newData[i][j] = this.data[j][i];
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return new Matrix(newData);
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}
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}
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