基本矩阵运算的Java实现

package pet.shop;
 
public class BasicMatrixMath {
  public final static int OPERATION_ADD = 1;
  public final static int OPERATION_SUB = 2;
  public final static int OPERATION_MUL = 4;
  
  /**
   * To be able to add two matrices, they must be of the same size
   * @param matrixa
   * @param matrixb
   */
  public int[][] add(int[][] matrixa, int[][] matrixb) {
    if(legalOperation(matrixa, matrixb, OPERATION_ADD)) {
      for(int i=0; i<matrixa.length; i++) {
        for(int j=0; j<matrixa[0].length; j++) {
          matrixa[i][j] = matrixa[i][j] + matrixb[i][j];
        }
      }
    }
    return matrixa;
  }
  
  /**
   * To be able to substract two matrices, they must be of the same size
   * 
   * @param matrixa
   * @param matrixb
   */
  public int[][] substract(int[][] matrixa, int[][] matrixb) {
    if(legalOperation(matrixa, matrixb, OPERATION_SUB)) {
      for(int i=0; i<matrixa.length; i++) {
        for(int j=0; j<matrixa[0].length; j++) {
          matrixa[i][j] = matrixa[i][j] - matrixb[i][j];
        }
      }
    }
    return matrixa;
  }
  
  /**
   * 
   * @param matrixa
   * @param matrixb
   */
  public int[][] multiplication(int[][] matrixa, int[][] matrixb) {
    if(legalOperation(matrixa, matrixb, OPERATION_SUB)) {
      int[][] result = new int[matrixa.length][matrixb[0].length];
      for(int i=0; i<matrixa.length; i++) {
        for(int j=0; j<matrixb[0].length; j++) {
          // i will complete this tomorrow @2012/09/17
          result[i][j] = calculateSingleResult(matrixa, matrixb, i, j); 
        }
      }
      return result;
    } 
    else
    {
      return null;
    }
  }
  
  private int calculateSingleResult(int[][] matrixa, int[][] matrixb, int row, int col) {
    int result = 0;
    for(int k=0; k<matrixa[0].length; k++) {
      result += matrixa[row][k] * matrixb[k][col];
    }
    return result;
  }
 
  /**
   * 
   * @param matrixa
   * @param b
   */
  public int[][] multiplication(int[][] matrixa, int b) {
    for(int i=0; i<matrixa.length; i++) {
      for(int j=0; j<matrixa[0].length; j++) {
        matrixa[i][j] = matrixa[i][j] * b;
      }
    }
    return matrixa;
  }
  
  /**
   * validate whether the parameters is valid parameters.
   * 
   * @param a
   * @param b
   * @param type
   * @return
   */
  private boolean legalOperation(int[][] a, int[][] b, int type) {
    boolean legal = true;
    if(type == OPERATION_ADD || type == OPERATION_SUB)
    {
      if(a.length != b.length || a[0].length != b[0].length) {
        legal = false;
      }
    } 
    else if(type == OPERATION_MUL)
    {
      if(a[0].length != b.length) {
        legal = false;
      }
    }
    return legal;
  }
  
  /**
   *  test code here !!!!
   * @param args
   */
  public static void main(String[] args) {
    int[][] a = new int[][]{{1,2},{3,4}};
    int[][] b = new int[][]{{7, 8}, {6, 5}};
    BasicMatrixMath bmm = new BasicMatrixMath();
    
    System.out.println("addition two matrix");
    int[][] result = bmm.add(a, b);
    for(int i=0; i<result.length; i++) {
      for(int j=0; j<result[0].length; j++) {
        System.out.print("\t" + result[i][j]);
      }
      System.out.println();
    }
    
    System.out.println("substract two matrix");
    result = bmm.substract(a, b);
    for(int i=0; i<result.length; i++) {
      for(int j=0; j<result[0].length; j++) {
        System.out.print("\t" + result[i][j]);
      }
      System.out.println();
    }
    
    System.out.println("multiplex one matrix");
    result = bmm.multiplication(a, 3);
    for(int i=0; i<result.length; i++) {
      for(int j=0; j<result[0].length; j++) {
        System.out.print("\t" + result[i][j]);
      }
      System.out.println();
    }
    
    System.out.println("multiplex two matrix");
    result = bmm.multiplication(a, b);
    for(int i=0; i<result.length; i++) {
      for(int j=0; j<result[0].length; j++) {
        System.out.print("\t" + result[i][j]);
      }
      System.out.println();
    } 
  }
}