Mega Code Archive
Demonstration of high-precision arithmetic with the BigDouble class
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/*
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");
}
}
}
}
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