BigDSqrt.java Source code

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Here is the source code for BigDSqrt.java

Source

/*
Java Programming for Engineers
Julio Sanchez
Maria P. Canton
    
    
ISBN: 0849308100
Publisher: CRC Press
*/

// Java for Engineers
//Filename: BigDSqrt
//Reference: Chapter 22
//Description:
//         Demonstration of high-precision arithmetic
//         with the BigDouble class. Program calculates the
//         square root of a floating-point number
//Requires:
//         Keyin class in current directory

import java.math.BigDecimal;

public class BigDSqrt {
    public static void main(String[] args) {
        double value = 1.0;
        String numS;
        int scale = 30;
        BigDecimal v;

        System.out.println("Big decimal square root routine\n");
        numS = Keyin.inString("Enter value: ");
        scale = Keyin.inInt("Enter scale: ");

        // Convert value to big decimal format
        v = new BigDecimal(numS);
        System.out.println(sqrt(v, scale));
    }

    public static BigDecimal sqrt(BigDecimal n, int s) {
        BigDecimal TWO = BigDecimal.valueOf(2);

        // Obtain the first approximation
        BigDecimal x = n.divide(BigDecimal.valueOf(3), s, BigDecimal.ROUND_DOWN);
        BigDecimal lastX = BigDecimal.valueOf(0);

        // Proceed through 50 iterations
        for (int i = 0; i < 50; i++) {
            x = n.add(x.multiply(x)).divide(x.multiply(TWO), s, BigDecimal.ROUND_DOWN);
            if (x.compareTo(lastX) == 0)
                break;
            lastX = x;
        }
        return x;
    }
}

//**********************************************************
//**********************************************************
//Program: Keyin
//Reference: Session 20
//Topics:
//1. Using the read() method of the ImputStream class
//in the java.io package
//2. Developing a class for performing basic console
//input of character and numeric types
//**********************************************************
//**********************************************************

class Keyin {

    //*******************************
    //   support methods
    //*******************************
    //Method to display the user's prompt string
    public static void printPrompt(String prompt) {
        System.out.print(prompt + " ");
        System.out.flush();
    }

    //Method to make sure no data is available in the
    //input stream
    public static void inputFlush() {
        int dummy;
        int bAvail;

        try {
            while ((System.in.available()) != 0)
                dummy = System.in.read();
        } catch (java.io.IOException e) {
            System.out.println("Input error");
        }
    }

    //********************************
    //  data input methods for
    //string, int, char, and double
    //********************************
    public static String inString(String prompt) {
        inputFlush();
        printPrompt(prompt);
        return inString();
    }

    public static String inString() {
        int aChar;
        String s = "";
        boolean finished = false;

        while (!finished) {
            try {
                aChar = System.in.read();
                if (aChar < 0 || (char) aChar == '\n')
                    finished = true;
                else if ((char) aChar != '\r')
                    s = s + (char) aChar; // Enter into string
            }

            catch (java.io.IOException e) {
                System.out.println("Input error");
                finished = true;
            }
        }
        return s;
    }

    public static int inInt(String prompt) {
        while (true) {
            inputFlush();
            printPrompt(prompt);
            try {
                return Integer.valueOf(inString().trim()).intValue();
            }

            catch (NumberFormatException e) {
                System.out.println("Invalid input. Not an integer");
            }
        }
    }

    public static char inChar(String prompt) {
        int aChar = 0;

        inputFlush();
        printPrompt(prompt);

        try {
            aChar = System.in.read();
        }

        catch (java.io.IOException e) {
            System.out.println("Input error");
        }
        inputFlush();
        return (char) aChar;
    }

    public static double inDouble(String prompt) {
        while (true) {
            inputFlush();
            printPrompt(prompt);
            try {
                return Double.valueOf(inString().trim()).doubleValue();
            }

            catch (NumberFormatException e) {
                System.out.println("Invalid input. Not a floating point number");
            }
        }
    }
}