Main.java Source code

Introduction

Here is the source code for Main.java

Source

//package com.java2s;

public class Main {
    private static final double LN10 = 2.30258509299404568401799145468;
    private static final int STR_NAN_LEN = 3;
    private static final String STR_NAN = "NaN";
    private static final int STR_INFINITY_LEN = 8;
    private static final String STR_INFINITY = "Infinity";

    static int getDoubleChars(double number, char[] buf, int charPos) {
        return getDoubleChars(number, buf, charPos, 17);
    }

    private static int getDoubleChars(double number, char[] buf, int charPos, int significantDigits) {
        if (number != number) {
            STR_NAN.getChars(0, STR_NAN_LEN, buf, charPos);
            return charPos + STR_NAN_LEN;
        }

        //we need to detect -0.0 to be compatible with JDK
        boolean negative = (Double.doubleToRawLongBits(number) & 0x8000000000000000L) != 0;
        if (negative) {
            buf[charPos++] = '-';
            number = -number;
        }

        if (number == Double.POSITIVE_INFINITY) {
            STR_INFINITY.getChars(0, STR_INFINITY_LEN, buf, charPos);
            return charPos + STR_INFINITY_LEN;
        }

        if (number == 0) {
            buf[charPos++] = '0';
            buf[charPos++] = '.';
            buf[charPos++] = '0';
        } else {
            int exponent = 0;

            // calc. the power (base 10) for the given number:
            int pow = (int) Math.floor(Math.log(number) / LN10);

            // use exponential formatting if number too big or too small
            if (pow < -3 || pow > 6) {
                exponent = pow;
                number /= Math.exp(LN10 * exponent);
            } // if

            // Recalc. the pow if exponent removed and d has changed
            pow = (int) Math.floor(Math.log(number) / LN10);

            // Decide how many insignificant zeros there will be in the
            // lead of the number.
            int insignificantDigits = -Math.min(0, pow);

            // Force it to start with at least "0." if necessarry
            pow = Math.max(0, pow);
            double divisor = Math.pow(10, pow);

            // Loop over the significant digits (17 for double, 8 for float)
            for (int i = 0, end = significantDigits + insignificantDigits, div; i < end; i++) {

                // Add the '.' when passing from 10^0 to 10^-1
                if (pow == -1) {
                    buf[charPos++] = '.';
                } // if

                // Find the divisor
                div = (int) (number / divisor);
                // This might happen with 1e6: pow = 5 ( instead of 6 )
                if (div == 10) {
                    buf[charPos++] = '1';
                    buf[charPos++] = '0';
                } // if
                else {
                    buf[charPos] = (char) (div + '0');
                    charPos++;
                } // else

                number -= div * divisor;
                divisor /= 10.0;
                pow--;

                // Break the loop if we have passed the '.'
                if (number == 0 && divisor < 0.1)
                    break;
            } // for

            // Remove trailing zeros
            while (buf[charPos - 1] == '0')
                charPos--;

            // Avoid "4." instead of "4.0"
            if (buf[charPos - 1] == '.')
                charPos++;
            if (exponent != 0) {
                buf[charPos++] = 'E';
                if (exponent < 0) {
                    buf[charPos++] = '-';
                    exponent = -exponent;
                }
                if (exponent >= 100)
                    buf[charPos++] = (char) (exponent / 100 + '0');
                if (exponent >= 10)
                    buf[charPos++] = (char) (exponent / 10 % 10 + '0');
                buf[charPos++] = (char) (exponent % 10 + '0');
            } // if
        }
        return charPos;
    }
}