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I am new to coding! If you find this question silly then I beg your pardon at the beginning! I was trying to solve Bisection Method using java. And I successfully did it! I took user input for initial guess 'a' and 'b'! In my code I created a method that stores the "f(x) = x^3 - x - 1" and when I call this method it solves the bisection method as per my given instructions.

  • The problem is I want to take the f(x) from user and use it like a formula.
  • I tried to take f(x) as String once but then what next? How can I form it into a formula?
  • Another problem is I cannot use '^' sign as power, I am currently using Math.pow(x,pow); Is there any way to make it('^') work as power?
  • If user gives input "3x^2 - 2x - 6", how am I supposed to make the program realize that the given equation indicates (assuming x = 4) "3*4^2 - 2*4 - 6", Not "34^2 - 24 - 6" !

I went through many answers but they couldn't satisfy me! I am adding my program below, if anyone can check kindly!

//Bisection Method

package numericalMethods;

import java.util.*;

public class BisectionMethod {

    public static void main(String[] args) {


        double a, b, c;

        Scanner sc = new Scanner(System.in);

        System.out.print("Enter value of a : ");
        a = sc.nextDouble();
        System.out.print("Enter value of b : ");
        b = sc.nextDouble();
        System.out.print("Enter maximum iteration : ");
        c = sc.nextDouble();

        System.out.println();



        if ((f(a) < 0 && f(b) > 0) || (f(a) > 0 && f(b) < 0)) {

            for(int i = 1; i <= c; i++){

                System.out.println("*** For iteration " + i + " ***");
                System.out.println("a is a = " + a + " and b is b = " + b);
                System.out.println("So f(a) is f(a) = " + f(a) + " and " + "f(b) is f(b) = " + f(b));

                //declaration and calculation of root variable
                double x = (a+b)/2;

                System.out.println("For iteration " + i + " root is x = " + x);
                System.out.println("And f(x) is f(x) = " + f(x));
                System.out.println("Here f(a)*f(x) = " + (f(a) * f(x)) );

                //Condition for assignment of the value of root x!
                if(f(a)*f(x) < 0){
                    b = x;
                    System.out.println("As f(a)*f(x) < 0, we assign value of x to b.");
                    System.out.println("So now a and b are respectively, a = "+ a + " and b = " + b);
                    System.out.println();
                }else if (f(a)*f(x) >0) {
                    a = x;
                    System.out.println("As f(a)*f(x) > 0, we assign value of x to a.");
                    System.out.println("Now a and b are respectively, a = "+ a + " and b = " + b);
                    System.out.println();
                }
            }
        }else {
            System.out.println("The condition was not fullfilled!");
        }


    }

    //declares function
    public static double f(double x){
        return ((x*x*x)-x-4);

    }

}
tasfi
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1 Answers1

1

You can use the ScriptEngineManager to evaluate mathematical expressions using the javascript engine.

ofc. you would need to replace "x" with it's substitute first: 

String formula = "x/2 + x";
Integer X = 6;

ScriptEngineManager mgr = new ScriptEngineManager();
ScriptEngine eng = mgr.getEngineByName("JavaScript");

System.out.println(eng.eval(formula.replace("x", X)));

But your question looks like "Homework", so i doubt this solution would be acceptable.

dognose
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