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GeezerVison is showing github.com — Java/Data Structures/Matrix/Matrix.java at master · allel/Java

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