http://poi.apache.org/: Apache POI - Java API To Access Microsoft Format Files (Apache Software Foundation) 
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package org.apache.poi.ss.util;



Excel converts numbers to text with different rules to those of java, so
 Double.toString(value) won't do.

    

  • No more than 15 significant figures are output (java does 18).
    • 

  • The sign char for the exponent is included even if positive
    • 

  • Special values (NaN and Infinity) get rendered like the ordinary
number that the bit pattern represents.
    • 

  • Denormalised values (between ±2-1074 and ±2-1022
 are displayed as "0"


IEEE 64-bit Double Rendering Comparison



Raw bitsJavaExcel


0x0000000000000000L0.00


0x3FF0000000000000L1.01


0x3FF00068DB8BAC71L1.00011.0001


0x4087A00000000000L756.0756


0x401E3D70A3D70A3DL7.567.56


0x405EDD3C07FB4C99L123.45678901234568123.456789012346


0x4132D687E3DF2180L1234567.89012345671234567.89012346


0x3EE9E409302678BAL1.2345678901234568E-51.23456789012346E-05


0x3F202E85BE180B74L1.2345678901234567E-40.000123456789012346


0x3F543A272D9E0E51L0.00123456789012345670.00123456789012346


0x3F8948B0F90591E6L0.0123456789012345680.0123456789012346


0x3EE9E409301B5A02L1.23456789E-50.0000123456789


0x3E6E7D05BDABDE50L5.6789012345E-80.000000056789012345


0x3E6E7D05BDAD407EL5.67890123456E-85.67890123456E-08


0x3E6E7D06029F18BEL5.678902E-80.00000005678902


0x2BCB5733CB32AE6EL9.999999999999123E-989.99999999999912E-98


0x2B617F7D4ED8C59EL1.0000000000001235E-991.0000000000001E-99


0x0036319916D67853L1.2345678901234578E-3071.2345678901235E-307


0x359DEE7A4AD4B81FL2.0E-502E-50


0x41678C29DCD6E9E0L1.2345678901234567E712345678.9012346


0x42A674E79C5FE523L1.2345678901234568E1312345678901234.6


0x42DC12218377DE6BL1.2345678901234567E14123456789012346


0x43118B54F22AEB03L1.2345678901234568E151234567890123460


0x43E56A95319D63E1L1.2345678901234567E1912345678901234600000


0x441AC53A7E04BCDAL1.2345678901234568E201.23456789012346E+20


0xC3E56A95319D63E1L-1.2345678901234567E19-12345678901234600000


0xC41AC53A7E04BCDAL-1.2345678901234568E20-1.23456789012346E+20


0x54820FE0BA17F46DL1.2345678901234577E991.2345678901235E+99


0x54B693D8E89DF188L1.2345678901234576E1001.2345678901235E+100


0x4A611B0EC57E649AL2.0E502E+50


0x7FEFFFFFFFFFFFFFL1.7976931348623157E3081.7976931348623E+308


0x0010000000000000L2.2250738585072014E-3082.2250738585072E-308


0x000FFFFFFFFFFFFFL2.225073858507201E-3080


0x0000000000000001L4.9E-3240


0x7FF0000000000000LInfinity1.7976931348623E+308


0xFFF0000000000000L-Infinity1.7976931348623E+308


0x441AC7A08EAD02F2L1.234999999999999E201.235E+20


0x40FE26BFFFFFFFF9L123499.9999999999123500


0x3E4A857BFB2F2809L1.234999999999999E-80.00000001235


0x3BCD291DEF868C89L1.234999999999999E-201.235E-20


0x444B1AE4D6E2EF4FL9.999999999999999E201E+21


0x412E847FFFFFFFFFL999999.99999999991000000


0x3E45798EE2308C39L9.999999999999999E-90.00000001


0x3C32725DD1D243ABL9.999999999999999E-190.000000000000000001


0x3BFD83C94FB6D2ABL9.999999999999999E-201E-19


0xC44B1AE4D6E2EF4FL-9.999999999999999E20-1E+21


0xC12E847FFFFFFFFFL-999999.9999999999-1000000


0xBE45798EE2308C39L-9.999999999999999E-9-0.00000001


0xBC32725DD1D243ABL-9.999999999999999E-19-0.000000000000000001


0xBBFD83C94FB6D2ABL-9.999999999999999E-20-1E-19


0xFFFF0420003C0000LNaN3.484840871308E+308


0x7FF8000000000000LNaN2.6965397022935E+308


0x7FFF0420003C0000LNaN3.484840871308E+308


0xFFF8000000000000LNaN2.6965397022935E+308


0xFFFF0AAAAAAAAAAALNaN3.4877119413344E+308


0x7FF80AAAAAAAAAAALNaN2.7012211948322E+308


0xFFFFFFFFFFFFFFFFLNaN3.5953862697246E+308


0x7FFFFFFFFFFFFFFFLNaN3.5953862697246E+308


0xFFF7FFFFFFFFFFFFLNaN2.6965397022935E+308



Note:
Excel has inconsistent rules for the following numeric operations:

    

  • Conversion to string (as handled here)
    • 

  • Rendering numerical quantities in the cell grid.
    • 

  • Conversion from text
    • 

  • General arithmetic
    • 


Excel's text to number conversion is not a true inverse of this operation.  The
allowable ranges are different.  Some numbers that don't correctly convert to text actually
do get handled properly when used in arithmetic evaluations.

Author:Josh Micich
/**
 * Excel converts numbers to text with different rules to those of java, so
 *  <code>Double.toString(value)</tt> won't do.
 * <ul>
 * <li>No more than 15 significant figures are output (java does 18).</li>
 * <li>The sign char for the exponent is included even if positive</li>
 * <li>Special values (<tt>NaN</tt> and <tt>Infinity</tt>) get rendered like the ordinary
 * number that the bit pattern represents.</li>
 * <li>Denormalised values (between &plusmn;2<sup>-1074</sup> and &plusmn;2<sup>-1022</sup>
 *  are displayed as "0"</sup>
 * </ul>
 * IEEE 64-bit Double Rendering Comparison
 *
 * <table border="1" cellpadding="2" cellspacing="0" summary="IEEE 64-bit Double Rendering Comparison">
 * <tr><th>Raw bits</th><th>Java</th><th>Excel</th></tr>
 *
 * <tr><td>0x0000000000000000L</td><td>0.0</td><td>0</td></tr>
 * <tr><td>0x3FF0000000000000L</td><td>1.0</td><td>1</td></tr>
 * <tr><td>0x3FF00068DB8BAC71L</td><td>1.0001</td><td>1.0001</td></tr>
 * <tr><td>0x4087A00000000000L</td><td>756.0</td><td>756</td></tr>
 * <tr><td>0x401E3D70A3D70A3DL</td><td>7.56</td><td>7.56</td></tr>
 * <tr><td>0x405EDD3C07FB4C99L</td><td>123.45678901234568</td><td>123.456789012346</td></tr>
 * <tr><td>0x4132D687E3DF2180L</td><td>1234567.8901234567</td><td>1234567.89012346</td></tr>
 * <tr><td>0x3EE9E409302678BAL</td><td>1.2345678901234568E-5</td><td>1.23456789012346E-05</td></tr>
 * <tr><td>0x3F202E85BE180B74L</td><td>1.2345678901234567E-4</td><td>0.000123456789012346</td></tr>
 * <tr><td>0x3F543A272D9E0E51L</td><td>0.0012345678901234567</td><td>0.00123456789012346</td></tr>
 * <tr><td>0x3F8948B0F90591E6L</td><td>0.012345678901234568</td><td>0.0123456789012346</td></tr>
 * <tr><td>0x3EE9E409301B5A02L</td><td>1.23456789E-5</td><td>0.0000123456789</td></tr>
 * <tr><td>0x3E6E7D05BDABDE50L</td><td>5.6789012345E-8</td><td>0.000000056789012345</td></tr>
 * <tr><td>0x3E6E7D05BDAD407EL</td><td>5.67890123456E-8</td><td>5.67890123456E-08</td></tr>
 * <tr><td>0x3E6E7D06029F18BEL</td><td>5.678902E-8</td><td>0.00000005678902</td></tr>
 * <tr><td>0x2BCB5733CB32AE6EL</td><td>9.999999999999123E-98</td><td>9.99999999999912E-98</td></tr>
 * <tr><td>0x2B617F7D4ED8C59EL</td><td>1.0000000000001235E-99</td><td>1.0000000000001E-99</td></tr>
 * <tr><td>0x0036319916D67853L</td><td>1.2345678901234578E-307</td><td>1.2345678901235E-307</td></tr>
 * <tr><td>0x359DEE7A4AD4B81FL</td><td>2.0E-50</td><td>2E-50</td></tr>
 * <tr><td>0x41678C29DCD6E9E0L</td><td>1.2345678901234567E7</td><td>12345678.9012346</td></tr>
 * <tr><td>0x42A674E79C5FE523L</td><td>1.2345678901234568E13</td><td>12345678901234.6</td></tr>
 * <tr><td>0x42DC12218377DE6BL</td><td>1.2345678901234567E14</td><td>123456789012346</td></tr>
 * <tr><td>0x43118B54F22AEB03L</td><td>1.2345678901234568E15</td><td>1234567890123460</td></tr>
 * <tr><td>0x43E56A95319D63E1L</td><td>1.2345678901234567E19</td><td>12345678901234600000</td></tr>
 * <tr><td>0x441AC53A7E04BCDAL</td><td>1.2345678901234568E20</td><td>1.23456789012346E+20</td></tr>
 * <tr><td>0xC3E56A95319D63E1L</td><td>-1.2345678901234567E19</td><td>-12345678901234600000</td></tr>
 * <tr><td>0xC41AC53A7E04BCDAL</td><td>-1.2345678901234568E20</td><td>-1.23456789012346E+20</td></tr>
 * <tr><td>0x54820FE0BA17F46DL</td><td>1.2345678901234577E99</td><td>1.2345678901235E+99</td></tr>
 * <tr><td>0x54B693D8E89DF188L</td><td>1.2345678901234576E100</td><td>1.2345678901235E+100</td></tr>
 * <tr><td>0x4A611B0EC57E649AL</td><td>2.0E50</td><td>2E+50</td></tr>
 * <tr><td>0x7FEFFFFFFFFFFFFFL</td><td>1.7976931348623157E308</td><td>1.7976931348623E+308</td></tr>
 * <tr><td>0x0010000000000000L</td><td>2.2250738585072014E-308</td><td>2.2250738585072E-308</td></tr>
 * <tr><td>0x000FFFFFFFFFFFFFL</td><td>2.225073858507201E-308</td><td>0</td></tr>
 * <tr><td>0x0000000000000001L</td><td>4.9E-324</td><td>0</td></tr>
 * <tr><td>0x7FF0000000000000L</td><td>Infinity</td><td>1.7976931348623E+308</td></tr>
 * <tr><td>0xFFF0000000000000L</td><td>-Infinity</td><td>1.7976931348623E+308</td></tr>
 * <tr><td>0x441AC7A08EAD02F2L</td><td>1.234999999999999E20</td><td>1.235E+20</td></tr>
 * <tr><td>0x40FE26BFFFFFFFF9L</td><td>123499.9999999999</td><td>123500</td></tr>
 * <tr><td>0x3E4A857BFB2F2809L</td><td>1.234999999999999E-8</td><td>0.00000001235</td></tr>
 * <tr><td>0x3BCD291DEF868C89L</td><td>1.234999999999999E-20</td><td>1.235E-20</td></tr>
 * <tr><td>0x444B1AE4D6E2EF4FL</td><td>9.999999999999999E20</td><td>1E+21</td></tr>
 * <tr><td>0x412E847FFFFFFFFFL</td><td>999999.9999999999</td><td>1000000</td></tr>
 * <tr><td>0x3E45798EE2308C39L</td><td>9.999999999999999E-9</td><td>0.00000001</td></tr>
 * <tr><td>0x3C32725DD1D243ABL</td><td>9.999999999999999E-19</td><td>0.000000000000000001</td></tr>
 * <tr><td>0x3BFD83C94FB6D2ABL</td><td>9.999999999999999E-20</td><td>1E-19</td></tr>
 * <tr><td>0xC44B1AE4D6E2EF4FL</td><td>-9.999999999999999E20</td><td>-1E+21</td></tr>
 * <tr><td>0xC12E847FFFFFFFFFL</td><td>-999999.9999999999</td><td>-1000000</td></tr>
 * <tr><td>0xBE45798EE2308C39L</td><td>-9.999999999999999E-9</td><td>-0.00000001</td></tr>
 * <tr><td>0xBC32725DD1D243ABL</td><td>-9.999999999999999E-19</td><td>-0.000000000000000001</td></tr>
 * <tr><td>0xBBFD83C94FB6D2ABL</td><td>-9.999999999999999E-20</td><td>-1E-19</td></tr>
 * <tr><td>0xFFFF0420003C0000L</td><td>NaN</td><td>3.484840871308E+308</td></tr>
 * <tr><td>0x7FF8000000000000L</td><td>NaN</td><td>2.6965397022935E+308</td></tr>
 * <tr><td>0x7FFF0420003C0000L</td><td>NaN</td><td>3.484840871308E+308</td></tr>
 * <tr><td>0xFFF8000000000000L</td><td>NaN</td><td>2.6965397022935E+308</td></tr>
 * <tr><td>0xFFFF0AAAAAAAAAAAL</td><td>NaN</td><td>3.4877119413344E+308</td></tr>
 * <tr><td>0x7FF80AAAAAAAAAAAL</td><td>NaN</td><td>2.7012211948322E+308</td></tr>
 * <tr><td>0xFFFFFFFFFFFFFFFFL</td><td>NaN</td><td>3.5953862697246E+308</td></tr>
 * <tr><td>0x7FFFFFFFFFFFFFFFL</td><td>NaN</td><td>3.5953862697246E+308</td></tr>
 * <tr><td>0xFFF7FFFFFFFFFFFFL</td><td>NaN</td><td>2.6965397022935E+308</td></tr>
 * </table>
 *
 * <b>Note</b>:
 * Excel has inconsistent rules for the following numeric operations:
 * <ul>
 * <li>Conversion to string (as handled here)</li>
 * <li>Rendering numerical quantities in the cell grid.</li>
 * <li>Conversion from text</li>
 * <li>General arithmetic</li>
 * </ul>
 * Excel's text to number conversion is not a true <i>inverse</i> of this operation.  The
 * allowable ranges are different.  Some numbers that don't correctly convert to text actually
 * <b>do</b> get handled properly when used in arithmetic evaluations.
 *
 * @author Josh Micich
 */
public final class NumberToTextConverter {

	private static final long EXCEL_NAN_BITS = 0xFFFF0420003C0000L;
	private static final int MAX_TEXT_LEN = 20;

	private NumberToTextConverter() {
		// no instances of this class
	}

	
Converts the supplied value to the text representation that Excel would give if
the value were to appear in an unformatted cell, or as a literal number in a formula.

Note - the results from this method differ slightly from those of Double.toString()
In some special cases Excel behaves quite differently.  This function attempts to reproduce
those results.

/**
	 * Converts the supplied <tt>value</tt> to the text representation that Excel would give if
	 * the value were to appear in an unformatted cell, or as a literal number in a formula.<br>
	 * Note - the results from this method differ slightly from those of <tt>Double.toString()</tt>
	 * In some special cases Excel behaves quite differently.  This function attempts to reproduce
	 * those results.
	 */
	public static String toText(double value) {
		return rawDoubleBitsToText(Double.doubleToLongBits(value));
	}
	/* package */ static String rawDoubleBitsToText(long pRawBits) {

		long rawBits = pRawBits;
		boolean isNegative = rawBits < 0; // sign bit is in the same place for long and double
		if (isNegative) {
			rawBits &= 0x7FFFFFFFFFFFFFFFL;
		}
		if (rawBits == 0) {
			return isNegative ? "-0" : "0";
		}
		ExpandedDouble ed = new ExpandedDouble(rawBits);
		if (ed.getBinaryExponent() < -1022) {
			// value is 'denormalised' which means it is less than 2^-1022
			// excel displays all these numbers as zero, even though calculations work OK
			return isNegative ? "-0" : "0";
		}
		if (ed.getBinaryExponent() == 1024) {
			// Special number NaN /Infinity
			// Normally one would not create HybridDecimal objects from these values
			// except in these cases Excel really tries to render them as if they were normal numbers
			if(rawBits == EXCEL_NAN_BITS) {
				return "3.484840871308E+308";
			}
			// This is where excel really gets it wrong
			// Special numbers like Infinity and NaN are interpreted according to
			// the standard rules below.
			isNegative = false; // except that the sign bit is ignored
		}
		NormalisedDecimal nd = ed.normaliseBaseTen();
		StringBuilder sb = new StringBuilder(MAX_TEXT_LEN+1);
		if (isNegative) {
			sb.append('-');
		}
		convertToText(sb, nd);
		return sb.toString();
	}
	private static void convertToText(StringBuilder sb, NormalisedDecimal pnd) {
		NormalisedDecimal rnd = pnd.roundUnits();
		int decExponent = rnd.getDecimalExponent();
		String decimalDigits;
		if (Math.abs(decExponent)>98) {
			decimalDigits = rnd.getSignificantDecimalDigitsLastDigitRounded();
			if (decimalDigits.length() == 16) {
				// rounding caused carry
				decExponent++;
			}
		} else {
			decimalDigits = rnd.getSignificantDecimalDigits();
		}
		int countSigDigits = countSignifantDigits(decimalDigits);
		if (decExponent < 0) {
			formatLessThanOne(sb, decimalDigits, decExponent, countSigDigits);
		} else {
			formatGreaterThanOne(sb, decimalDigits, decExponent, countSigDigits);
		}
	}

	private static void formatLessThanOne(StringBuilder sb, String decimalDigits, int decExponent,
			int countSigDigits) {
		int nLeadingZeros = -decExponent - 1;
		int normalLength = 2 + nLeadingZeros + countSigDigits; // 2 == "0.".length()

		if (needsScientificNotation(normalLength)) {
			sb.append(decimalDigits.charAt(0));
			if (countSigDigits > 1) {
    			sb.append('.');
    			sb.append(decimalDigits.subSequence(1, countSigDigits));
			}
			sb.append("E-");
			appendExp(sb, -decExponent);
			return;
		}
		sb.append("0.");
		for (int i=nLeadingZeros; i>0; i--) {
			sb.append('0');
		}
		sb.append(decimalDigits.subSequence(0, countSigDigits));
	}

	private static void formatGreaterThanOne(StringBuilder sb, String decimalDigits, int decExponent, int countSigDigits) {

		if (decExponent > 19) {
			// scientific notation
			sb.append(decimalDigits.charAt(0));
			if (countSigDigits>1) {
				sb.append('.');
				sb.append(decimalDigits.subSequence(1, countSigDigits));
			}
			sb.append("E+");
			appendExp(sb, decExponent);
			return;
		}
		int nFractionalDigits = countSigDigits - decExponent-1;
		if (nFractionalDigits > 0) {
			sb.append(decimalDigits.subSequence(0, decExponent+1));
			sb.append('.');
			sb.append(decimalDigits.subSequence(decExponent+1, countSigDigits));
			return;
		}
		sb.append(decimalDigits.subSequence(0, countSigDigits));
		for (int i=-nFractionalDigits; i>0; i--) {
			sb.append('0');
		}
	}

	private static boolean needsScientificNotation(int nDigits) {
		return nDigits > MAX_TEXT_LEN;
	}

	private static int countSignifantDigits(String sb) {
		int result=sb.length()-1;
		while(sb.charAt(result) == '0') {
			result--;
			if(result < 0) {
				throw new RuntimeException("No non-zero digits found");
			}
		}
		return result + 1;
	}

	private static void appendExp(StringBuilder sb, int val) {
		if(val < 10) {
			sb.append('0');
			sb.append((char)('0' + val));
			return;
		}
		sb.append(val);
	}
}