equationsolver.java

Java程序设计技巧与开发实例附书源代码。

public class EquationSolver {
   public static void swapRows(double matrix[][], int row1, int row2) {
      for (int col = 0; col < matrix[row1].length; col++) {
         double tmp = matrix[row1][col];
         matrix[row1][col] = matrix[row2][col];
         matrix[row2][col] = tmp;
      }
   }

   public static void multRow(double matrix[][], double number, int row) {
      for (int col = 0; col < matrix[row].length; col++) {
         matrix[row][col] *= number;
      }
   }

   public static void addRows(double matrix[][], double num, int row1, int row2) {
      for (int col = 0; col < matrix[row1].length; col++) {
         matrix[row2][col] += num * matrix[row1][col];
      }
   }

   public static boolean foundNonZeroDiag(double matrix[][], int diag) {
      for (int row = diag; row < matrix.length; row++) {
         if (matrix[row][diag] != 0) {
            swapRows(matrix, row, diag);
            return true;
         }
      }
      return false;
   }

   public static void normalizeColumn(double matrix[][], int col) {
      multRow(matrix, 1.0 / matrix[col][col], col);
      for (int row = 0; row < matrix.length; row++) {
         if (row != col) {
            addRows(matrix, -matrix[row][col], col, row);
         }
      }
   }

   public static boolean normalizeMatrix(double matrix[][]) {
      for (int col = 0; col < matrix.length; col++) {
         if (foundNonZeroDiag(matrix, col)) {
            normalizeColumn(matrix, col);
         }
         else {
            return false;
         }
      }
      return true;
   }

   public static void showMatrix(double matrix[][]) {
      for (int row = 0; row < matrix.length; row++) {
         for (int col = 0; col < matrix[row].length; col++) {
            System.out.print(matrix[row][col] + "\t");
         }
         System.out.print("\n");
      }
      System.out.print("\n");
   }

   public static double[][] createMatrix() {
      System.out.print("Enter number of variables: ");
      int numVars = Console.readInt();
      double matrix[][] = new double[numVars][numVars + 1];
      for (int row = 0; row < numVars; row++) {
         for (int col = 0; col < numVars; col++) {
            System.out.print("Coefficient row " + (row + 1) +
                             ", column " + (col + 1) + ": ");
            matrix[row][col] = Console.readDouble();
         }
         System.out.print("Right-hand side for row " + (row + 1) + ": ");
         matrix[row][numVars] = Console.readDouble();
      }
      return matrix;
   }

   public static void main(String args[]) {
      double matrix[][] = createMatrix();
      showMatrix(matrix);
      if (normalizeMatrix(matrix)) {
         showMatrix(matrix);
      }
      else {
         System.out.println("No solution or no unique solution");
      }
   }
}