Java/Data Type/BigDouble

Demonstration of high-precision arithmetic with the BigDouble class

   <source lang="java">

/* 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.rupareTo(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");
     }
   }
 }

}

      </source>