VL-Programmieren/VL08/Aufgabe03/Matrix.java

package VL08.Aufgabe03;

/**
 * A class to represent a Matrix.
 */
public class Matrix {
  private int rows = 0;
  private int columns = 0;
  private int[][] matrix;

  Matrix(int rows, int columns) {
    this.rows = rows;
    this.columns = columns;
    this.matrix = new int[this.rows][this.columns];

    for (int rowIndex = 0; rowIndex < this.rows; rowIndex++) {
      for (int columnIndex = 0; columnIndex < this.columns; columnIndex++) {
        this.matrix[rowIndex][columnIndex] = 0;
      }
    }
  }

  /**
   * Method to get the number of columns.
   *
   * @return The number of columns.
   */
  int getColumns() {
    return this.columns;
  }

  /**
   * Method to get the number of rows.
   *
   * @return The number of rows.
   */
  int getRows() {
    return this.rows;
  }

  /**
   * Method to get the value of a specific field.
   *
   * @param row    The row of the value.
   * @param column The column of the value.
   * @return The value of the given row and column.
   */
  int getValue(int row, int column) {
    return this.matrix[row][column];
  }

  /**
   * Method to set the value of a specific field.
   *
   * @param row    The row to set the value.
   * @param column The column to set the value.
   * @param value  The value to be set in the field.
   */
  void setValue(int row, int column, int value) {
    this.matrix[row][column] = value;
  }

  /**
   * Methode to get the state whether the given Matrix is same size.
   *
   * @param matrix The Matrix to check for same size.
   * @return The state whether the given Matrix is same size.
   */
  boolean isSameSize(Matrix matrix) {
    return (this.rows == matrix.getRows()) && (this.columns == matrix.getColumns());
  }

  /**
   * Method to add a Matrix to the current Matrix.
   *
   * @param matrix The Matrix to add to the current Matrix.
   */
  void add(Matrix matrix) {
    if (!this.isSameSize(matrix)) {
      return;
    }

    for (int rowIndex = 0; rowIndex < this.rows; rowIndex++) {
      for (int columnIndex = 0; columnIndex < this.columns; columnIndex++) {
        this.matrix[rowIndex][columnIndex] += matrix.getValue(rowIndex, columnIndex);
      }
    }
  }

  /**
   * Method to multiply a scalar value to the Matrix.
   *
   * @param scalar The scalar value to multiply the Matrix.
   */
  void multiply(int scalar) {
    for (int rowIndex = 0; rowIndex < this.rows; rowIndex++) {
      for (int columnIndex = 0; columnIndex < this.columns; columnIndex++) {
        this.matrix[rowIndex][columnIndex] *= scalar;
      }
    }
  }

  /**
   * Method to multiply a Matrix to the Matrix.
   *
   * @param matrix The Matrix to multiply with this Matrix.
   * @return State whether the multiplication of the Matrix was successful.
   */
  boolean multiply(Matrix matrix) {

    // multiplication is not possible if there are no rows or no columns.
    if (this.getColumns() == 0 || this.getRows() == 0) {
      return false;
    }

    // multiplication is only possible if the number of rows of Matrix A
    // is equals to the number of columns of Matrix B.
    if (this.getColumns() != matrix.getRows()) {
      return false;
    }

    int[][] tempMatrix = new int[this.matrix.length][this.matrix.length];

    for (int rowIndex = 0; rowIndex < this.getRows(); rowIndex++) {
      for (int columnIndex = 0; columnIndex < matrix.getColumns(); columnIndex++) {
        tempMatrix[rowIndex][columnIndex] = 0;

        for (int fieldIndex = 0; fieldIndex < matrix.getRows(); fieldIndex++) {
          tempMatrix[rowIndex][columnIndex] += this.getValue(rowIndex, fieldIndex)
              * matrix.getValue(fieldIndex, columnIndex);
        }
      }
    }

    this.matrix = tempMatrix;
    this.columns = tempMatrix.length;
    this.rows = tempMatrix.length;

    return true;
  }

  /**
   * Method to print the Matrix.
   */
  void print() {
    for (int rowIndex = 0; rowIndex < this.rows; rowIndex++) {
      for (int columnIndex = 0; columnIndex < this.columns; columnIndex++) {
        System.out.printf("%5d", this.getValue(rowIndex, columnIndex));
      }

      System.out.print("\n");
    }
  }
}