javamathmatrixjamalinear-equation

Printing out: no solution, multiple solution with Apache in java


I have this code which give solution to 4x4 linear equations. how can i print out when a linear equation have no solution or have multiples ones. instead of prints error ?

public class OvaWork 
{


    void fourthEquationSolver()
    {
        //Creating  Arrays Representing Equations
        double[][] lhsArray = {{8,1,10,1}, {2,1,5,4}, {1,5,3,2}, {9,8,4,6}};
        double[] rhsArray = {14,22,38,44};
        //Creating Matrix Objects with arrays
        Matrix lhs = new Matrix(lhsArray);
        Matrix rhs = new Matrix(rhsArray, 4);
        //Calculate Solved Matrix
        Matrix ans = lhs.solve(rhs);
        //Printing Answers
        System.out.println("x1 = " + (ans.get(0, 0)));
        System.out.println("x2 = " + (ans.get(1, 0)));
        System.out.println("X3 = " + (ans.get(2, 0)));
        System.out.println("X4 = " + (ans.get(3, 0)));
    }



    public static void main(String[] args) 
    {
        OvaWork equation = new OvaWork();

    }
}

When i write into this code a matrix like this:

1,1,1,1=14
2,2,2,2=22
3,3,3,3=38
4,4,4,4=44

this code prints :

Exception in thread "main" java.lang.RuntimeException: Matrix is singular.
    at Jama.LUDecomposition.solve(LUDecomposition.java:282)
    at Jama.Matrix.solve(Matrix.java:815)
    at OvaWork.fourthEquationSolver(OvaWork.java:20)
    at OvaWork.main(OvaWork.java:106)

because the above matrix have or multiple solutions, or no have solution


Solution

  • You can ask for the determinant https://en.wikipedia.org/wiki/Determinant

    "A system of linear equations has a unique non-trivial solution if and only if its determinant is non-zero. If this determinant is zero, then the system has either no nontrivial solutions or an infinite number of solutions."

    http://math.oregonstate.edu/home/programs/undergrad/CalculusQuestStudyGuides/vcalc/system/system.html

    if (lhs.det() == 0) {
        System.out.println("No solution or infinite number of solutions");
    } else {
        Matrix ans = lhs.solve(rhs);
        //Printing Answers
        System.out.println("x1 = " + (ans.get(0, 0)));
        System.out.println("x2 = " + (ans.get(1, 0)));
        System.out.println("X3 = " + (ans.get(2, 0)));
        System.out.println("X4 = " + (ans.get(3, 0)));
    }