Is there a way of finding compound interest in java with inputs using JOptionPane?

Question

I've tried with the following inputs:

principal= 1000, rate=4, timesapplied=2(half-yearly), elapsedyears=2

import javax.swing.*;
import java.math.BigDecimal;

public class CICalc {
    public static void main(String[] args) {
        Double principal;
        Double rate;
        Double timesapplied;
        Double elapsedyears;

        principal= Double.parseDouble(JOptionPane.showInputDialog("Enter the principal amount"));
        rate=Double.parseDouble(JOptionPane.showInputDialog("Enter the Rate of Interest"));
        timesapplied=Double.parseDouble(JOptionPane.showInputDialog("Enter the number of times the principal is compounded"));
        elapsedyears=Double.parseDouble(JOptionPane.showInputDialog("Enter the amount of time(In years and if in months, write them in this format- month/12) the principal is being invested for"));

        BigDecimal CI;
        BigDecimal inf;
        inf= BigDecimal.valueOf(Math.pow(rate+(1/timesapplied*100),elapsedyears*timesapplied));

        CI= (BigDecimal.valueOf(principal)).multiply(inf);
        BigDecimal P= CI.subtract(BigDecimal.valueOf(principal));

        JOptionPane.showMessageDialog(null,"The Compound Interest for "+elapsedyears+" years is "+CI+"$ and the the interest gained is "+P+"$");

    }
}

Can someone please point out the mistakes and help me out? Actually, I had made this using only Double but the problem was that the result had way too many decimal points. So I had to use BigDecimal.

Answer 1

Actually, I had made this using only Double but the problem was that the result had way too many decimal points. So I had to use BigDecimal.

Use BigDecimal setScale​(int newScale, RoundingMode roundingMode) to round the result up to the required number of decimal places.

import java.math.BigDecimal;
import java.math.RoundingMode;

import javax.swing.JOptionPane;

class Main {
    public static void main(String[] args) {
        double principal = Double.parseDouble(JOptionPane.showInputDialog("Enter the principal amount"));
        double rate = Double.parseDouble(JOptionPane.showInputDialog("Enter the Rate of Interest"));
        double timesapplied = Double
                .parseDouble(JOptionPane.showInputDialog("Enter the number of times the principal is compounded"));
        double elapsedyears = Double.parseDouble(JOptionPane.showInputDialog("Enter the number of years"));

        double base = 1.0 + rate / (timesapplied * 100.0);
        double exponent = elapsedyears * timesapplied;

        double inf = Math.pow(base, exponent);
        double CI = principal * inf;
        double P = CI - principal;

        JOptionPane.showMessageDialog(null,
                "The Compound Interest for " + BigDecimal.valueOf(elapsedyears).setScale(2, RoundingMode.HALF_UP)
                        + " years is " + BigDecimal.valueOf(CI).setScale(2, RoundingMode.HALF_UP)
                        + "$ and the the interest gained is " + BigDecimal.valueOf(P).setScale(2, RoundingMode.HALF_UP)
                        + "$");
    }
}