jdk11 jdk12_JDK 12附带紧凑数字格式

jdk11 jdk12

JDK 12 Early Access Build 24引入了对紧凑数字格式的支持。 JDK-8188147（紧凑数字格式支持）CSR的“摘要”是简单的句子，“添加了对JDK中的紧凑/短数字格式的支持。” 同一CSR还提供了详细的“解决方案”部分，该部分提供了为每个语言环境以多种紧凑形式提供数字以及添加到JDK以支持该功能（新类，新枚举，新方法等）的构造/ API的背景。

每个语言环境中数字的紧凑和简短格式的表示均基于Unicode公共语言环境数据存储库（CLDR）。新添加的类java.text.CompactNumberFormat具有类级别的Javadoc注释，这些注释提供了大量有关如何以“短”和“长”紧凑型数字格式表示数字的详细信息。该类的Javadoc注释还指定了与自定义数字格式相关的紧凑数字模式，格式，解析和舍入（默认情况下为RoundingMode.HALF_EVEN ）。

Nishit Jain在要求审查对JDK 12添加紧凑数字格式的请求中写道：

现有的NumberFormat API为格式化和解析数字提供基于语言环境的支持，其中包括格式化小数，百分数，货币等，但是缺少将数字格式化为人类可读或紧凑形式的支持。此RFE添加了该功能，以紧凑格式格式化十进制数（例如，在en_US语言环境中为1000-> 1K，1000000-> 1M），这对于显示空间有限的环境很有用，因此可以显示格式化的字符串在那个有限的空间里。它是由LDML的紧凑数字格式规范定义的。

http://unicode.org/reports/tr35/tr35-numbers.html#Compact_Number_Formats

通过代码示例来了解紧凑的数字格式可能是最容易的。以下类（ CompactNumberFormatDemo ）是针对JDK 12 Early Access Build 24编译和执行的。

package dustin.examples.jdk12.format;  import static java.lang.System.out;  import java.text.NumberFormat;  
import java.util.Locale;  /** * Demonstrate Compact Number Format support added to * JDK 12 as of Early Access Build 24 (see also * JDK-8177552: Compact Number Formatting support). */  
public class CompactNumberFormatDemo  
{  private static void demonstrateCompactNumberFormatting(final long numberToFormat)  {  final NumberFormat numberFormatDefault  = NumberFormat.getCompactNumberInstance();  final NumberFormat numberFormatUsLong  = NumberFormat.getCompactNumberInstance(Locale.US, NumberFormat.Style.LONG);  final NumberFormat numberFormatUkShort  = NumberFormat.getCompactNumberInstance(Locale.UK, NumberFormat.Style.SHORT);  final NumberFormat numberFormatUkLong  = NumberFormat.getCompactNumberInstance(Locale.UK, NumberFormat.Style.LONG);  final NumberFormat numberFormatFrShort  = NumberFormat.getCompactNumberInstance(Locale.FRANCE, NumberFormat.Style.SHORT);  final NumberFormat numberFormatFrLong  = NumberFormat.getCompactNumberInstance(Locale.FRANCE, NumberFormat.Style.LONG);  final NumberFormat numberFormatGrShort  = NumberFormat.getCompactNumberInstance(Locale.GERMANY, NumberFormat.Style.SHORT);  final NumberFormat numberFormatGrLong  = NumberFormat.getCompactNumberInstance(Locale.GERMANY, NumberFormat.Style.LONG);  final NumberFormat numberFormatItShort  = NumberFormat.getCompactNumberInstance(Locale.ITALY, NumberFormat.Style.SHORT);  final NumberFormat numberFormatItLong  = NumberFormat.getCompactNumberInstance(Locale.ITALY, NumberFormat.Style.LONG);  out.println("Demonstrating Compact Number Formatting on '" + numberToFormat + "':");  out.println("\tDefault:  " + numberFormatDefault.format(numberToFormat));  out.println("\tUS/Long:  " + numberFormatUsLong.format(numberToFormat));  out.println("\tUK/Short: " + numberFormatUkShort.format(numberToFormat));  out.println("\tUK/Long:  " + numberFormatUkLong.format(numberToFormat));  out.println("\tFR/Short: " + numberFormatFrShort.format(numberToFormat));  out.println("\tFR/Long:  " + numberFormatFrLong.format(numberToFormat));  out.println("\tGR/Short: " + numberFormatGrShort.format(numberToFormat));  out.println("\tGR/Long:  " + numberFormatGrLong.format(numberToFormat));  out.println("\tIT/Short: " + numberFormatItShort.format(numberToFormat));  out.println("\tIT/Long:  " + numberFormatItLong.format(numberToFormat));  }  /** * Main demonstration executable. * @param arguments Command-line arguments: none expected. */  public static void main(final String[] arguments)  {  demonstrateCompactNumberFormatting(15);  demonstrateCompactNumberFormatting(150);  demonstrateCompactNumberFormatting(1500);  demonstrateCompactNumberFormatting(15000);  demonstrateCompactNumberFormatting(150000);  demonstrateCompactNumberFormatting(1500000);  demonstrateCompactNumberFormatting(15000000);  }  
}

执行后，以上代码将以下内容写入标准输出：

Demonstrating Compact Number Formatting on '15':Default:  15US/Long:  15UK/Short: 15UK/Long:  15FR/Short: 15FR/Long:  15GR/Short: 15GR/Long:  15IT/Short: 15IT/Long:  15
Demonstrating Compact Number Formatting on '150':Default:  150US/Long:  150UK/Short: 150UK/Long:  150FR/Short: 150FR/Long:  150GR/Short: 150GR/Long:  150IT/Short: 150IT/Long:  150
Demonstrating Compact Number Formatting on '1500':Default:  2KUS/Long:  2 thousandUK/Short: 2KUK/Long:  2 thousandFR/Short: 2 kFR/Long:  2 millierGR/Short: 1.500GR/Long:  2 TausendIT/Short: 1.500IT/Long:  2 mille
Demonstrating Compact Number Formatting on '15000':Default:  15KUS/Long:  15 thousandUK/Short: 15KUK/Long:  15 thousandFR/Short: 15 kFR/Long:  15 milleGR/Short: 15.000GR/Long:  15 TausendIT/Short: 15.000IT/Long:  15 mila
Demonstrating Compact Number Formatting on '150000':Default:  150KUS/Long:  150 thousandUK/Short: 150KUK/Long:  150 thousandFR/Short: 150 kFR/Long:  150 milleGR/Short: 150.000GR/Long:  150 TausendIT/Short: 150.000IT/Long:  150 mila
Demonstrating Compact Number Formatting on '1500000':Default:  2MUS/Long:  2 millionUK/Short: 2MUK/Long:  2 millionFR/Short: 2 MFR/Long:  2 millionGR/Short: 2 Mio.GR/Long:  2 MillionIT/Short: 2 MlnIT/Long:  2 milione
Demonstrating Compact Number Formatting on '15000000':Default:  15MUS/Long:  15 millionUK/Short: 15MUK/Long:  15 millionFR/Short: 15 MFR/Long:  15 millionGR/Short: 15 Mio.GR/Long:  15 MillionenIT/Short: 15 MlnIT/Long:  15 milioni

通过Early Access Build 24添加到JDK 12的紧凑数字格式支持允许格式化和解析以语言环境特定的“长”或“短”紧凑形式的数字表示形式。