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8159023: Engineering notation of DecimalFormat does not work as documented

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Reviewed-by: naoto
This commit is contained in:
Justin Lu 2023-05-25 21:54:58 +00:00
parent ee321c70e5
commit 46c4da7fdd
2 changed files with 147 additions and 7 deletions
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49
src/java.base/share/classes/java/text/DecimalFormat.java
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@ -264,6 +264,16 @@ import sun.util.locale.provider.ResourceBundleBasedAdapter;
* formatted using the localized minus sign, <em>not</em> the prefix and suffix
* from the pattern. This allows patterns such as {@code "0.###E0 m/s"}.
*
* <li>The <em>maximum integer</em> digits is the sum of '0's and '#'s
* prior to the decimal point. The <em>minimum integer</em> digits is the
* sum of the '0's prior to the decimal point. The <em>maximum fraction</em>
* and <em>minimum fraction</em> digits follow the same rules, but apply to the
* digits after the decimal point but before the exponent. For example, the
* following pattern: {@code "#00.0####E0"} would have a minimum number of
* integer digits = 2("00") and a maximum number of integer digits = 3("#00"). It
* would have a minimum number of fraction digits = 1("0") and a maximum number of fraction
* digits= 5("0####").
*
* <li>The minimum and maximum number of integer digits are interpreted
* together:
*
@ -282,13 +292,38 @@ import sun.util.locale.provider.ResourceBundleBasedAdapter;
* {@code "12.3E-4"}.
* </ul>
*
* <li>The number of significant digits in the mantissa is the sum of the
* <em>minimum integer</em> and <em>maximum fraction</em> digits, and is
* unaffected by the maximum integer digits. For example, 12345 formatted with
* {@code "##0.##E0"} is {@code "12.3E3"}. To show all digits, set
* the significant digits count to zero. The number of significant digits
* <li>For a given number, the amount of significant digits in
* the mantissa can be calculated as such
*
* <blockquote><pre>
* <i>Mantissa Digits:</i>
* min(max(Minimum Pattern Digits, Original Number Digits), Maximum Pattern Digits)
* <i>Minimum pattern Digits:</i>
* <i>Minimum Integer Digits</i> + <i>Minimum Fraction Digits</i>
* <i>Maximum pattern Digits:</i>
* <i>Maximum Integer Digits</i> + <i>Maximum Fraction Digits</i>
* <i>Original Number Digits:</i>
* The amount of significant digits in the number to be formatted
* </pre></blockquote>
*
* This means that generally, a mantissa will have up to the combined maximum integer
* and fraction digits, if the original number itself has enough significant digits. However,
* if there are more minimum pattern digits than significant digits in the original number,
* the mantissa will have significant digits that equals the combined
* minimum integer and fraction digits. The number of significant digits
* does not affect parsing.
*
* <p>It should be noted, that the integer portion of the mantissa will give
* any excess digits to the fraction portion, whether it be for precision or
* for satisfying the total amount of combined minimum digits.
*
* <p>This behavior can be observed in the following example,
* {@snippet lang=java :
* DecimalFormat df = new DecimalFormat("#000.000##E0");
* df.format(12); // returns "12.0000E0"
* df.format(123456789) // returns "1.23456789E8"
* }
*
* <li>Exponential patterns may not contain grouping separators.
* </ul>
*
@ -308,8 +343,8 @@ import sun.util.locale.provider.ResourceBundleBasedAdapter;
*
* <h4>Special Values</h4>
*
* <p>{@code NaN} is formatted as a string, which typically has a single character
* {@code U+FFFD}. This string is determined by the
* <p>Not a Number({@code NaN}) is formatted as a string, which typically has a
* single character {@code U+FFFD}. This string is determined by the
* {@code DecimalFormatSymbols} object. This is the only value for which
* the prefixes and suffixes are not used.
*