How to Solve Equations with java?

Question

I have three equations like the following ones:

• x + y + z = 100;
• x + y - z = 50;
• x - y - z = 10;

How can I find the values of x, y, and z with Java?

String equation1="x+y+z=100;";
String equation2="x+y-z=50;";
String equation3="x-y-z=10;";

int[] SolveEquations(equation1,equation2,equation3) {
   // to do
   // how to do?    
} 

Do you have any possible solutions or other common frameworks?

Answer 1

try this, please:

import org.apache.commons.math3.linear.*;
import org.junit.Assert;
import org.junit.Test;

/**
 * Author: Andrea Ciccotta
 */
public class LinearSystemTest extends Assert {

    /**
     * Ax = B
     * 2x + 3y - 2z = 1
     * -x + 7y + 6x = -2
     * 4x - 3y - 5z = 1
     * <p>
     * it will use the LUDecomposition:
     * LU decomposition:
     * 1. find A = LU where LUx = B
     * 2. solve Ly = B
     * 4. solve Ux = y
     */
    @Test
    public void linearSystem3x3Test() {
        final RealMatrix coefficients = new Array2DRowRealMatrix(new double[][]{{2, 3, -2}, {-1, 7, 6}, {4, -3, -5}});
        final DecompositionSolver solver = new LUDecomposition(coefficients).getSolver();

        final RealVector constants = new ArrayRealVector(new double[]{1, -2, 1}, false);
        final RealVector solution = solver.solve(constants);
        final double[] arraySolution = solution.toArray();

        assertEquals(arraySolution[0], -0.36986301369863006, 0);
        assertEquals(arraySolution[1], 0.1780821917808219, 0);
        assertEquals(arraySolution[2], -0.6027397260273972, 0);
    }

}

Answer 2

You can also use Commons Math. They have a section of this in their userguide (see 3.4)