我想将以下数字格式化为java旁边的数字：
1000 to 1k
5821 to 5.8k
10500 to 10k
101800 to 101k
2000000 to 2m
7800000 to 7.8m
92150000 to 92m
123200000 to 123m
右边的数字是长整数，左边的数字是字符串。 我应该如何处理这个问题。我已经为此做了很少的算法，但我认为可能已经发明了一些可以做得更好的事情，并且如果我开始处理数十亿和数万亿，则不需要额外的测试：）
附加要求：
答案 0 :(得分：127)
这是 一个适用于任何长值的解决方案 ，我发现它非常易读（核心逻辑在{{1}的底部三行中完成方法）。
利用format找到合适的后缀。令人惊讶的是，它比我之前编写的使用数组的解决方案更有效，并且更难以阅读。
TreeMapprivate static final NavigableMap<Long, String> suffixes = new TreeMap<> ();
static {
suffixes.put(1_000L, "k");
suffixes.put(1_000_000L, "M");
suffixes.put(1_000_000_000L, "G");
suffixes.put(1_000_000_000_000L, "T");
suffixes.put(1_000_000_000_000_000L, "P");
suffixes.put(1_000_000_000_000_000_000L, "E");
}
public static String format(long value) {
//Long.MIN_VALUE == -Long.MIN_VALUE so we need an adjustment here
if (value == Long.MIN_VALUE) return format(Long.MIN_VALUE + 1);
if (value < 0) return "-" + format(-value);
if (value < 1000) return Long.toString(value); //deal with easy case
Entry<Long, String> e = suffixes.floorEntry(value);
Long divideBy = e.getKey();
String suffix = e.getValue();
long truncated = value / (divideBy / 10); //the number part of the output times 10
boolean hasDecimal = truncated < 100 && (truncated / 10d) != (truncated / 10);
return hasDecimal ? (truncated / 10d) + suffix : (truncated / 10) + suffix;
}
答案 1 :(得分：92)
我知道，这看起来更像是一个C程序，但它超级轻巧！
public static void main(String args[]) {
long[] numbers = new long[]{1000, 5821, 10500, 101800, 2000000, 7800000, 92150000, 123200000, 9999999};
for(long n : numbers) {
System.out.println(n + " => " + coolFormat(n, 0));
}
}
private static char[] c = new char[]{'k', 'm', 'b', 't'};
/**
* Recursive implementation, invokes itself for each factor of a thousand, increasing the class on each invokation.
* @param n the number to format
* @param iteration in fact this is the class from the array c
* @return a String representing the number n formatted in a cool looking way.
*/
private static String coolFormat(double n, int iteration) {
double d = ((long) n / 100) / 10.0;
boolean isRound = (d * 10) %10 == 0;//true if the decimal part is equal to 0 (then it's trimmed anyway)
return (d < 1000? //this determines the class, i.e. 'k', 'm' etc
((d > 99.9 || isRound || (!isRound && d > 9.99)? //this decides whether to trim the decimals
(int) d * 10 / 10 : d + "" // (int) d * 10 / 10 drops the decimal
) + "" + c[iteration])
: coolFormat(d, iteration+1));
}
输出：
1000 => 1k
5821 => 5.8k
10500 => 10k
101800 => 101k
2000000 => 2m
7800000 => 7.8m
92150000 => 92m
123200000 => 123m
9999999 => 9.9m
答案 2 :(得分：42)
这是一个使用DecimalFormat工程符号的解决方案：
public static void main(String args[]) {
long[] numbers = new long[]{7, 12, 856, 1000, 5821, 10500, 101800, 2000000, 7800000, 92150000, 123200000, 9999999};
for(long number : numbers) {
System.out.println(number + " = " + format(number));
}
}
private static String[] suffix = new String[]{"","k", "m", "b", "t"};
private static int MAX_LENGTH = 4;
private static String format(double number) {
String r = new DecimalFormat("##0E0").format(number);
r = r.replaceAll("E[0-9]", suffix[Character.getNumericValue(r.charAt(r.length() - 1)) / 3]);
while(r.length() > MAX_LENGTH || r.matches("[0-9]+\\.[a-z]")){
r = r.substring(0, r.length()-2) + r.substring(r.length() - 1);
}
return r;
}
输出：
7 = 7
12 = 12
856 = 856
1000 = 1k
5821 = 5.8k
10500 = 10k
101800 = 102k
2000000 = 2m
7800000 = 7.8m
92150000 = 92m
123200000 = 123m
9999999 = 10m
答案 3 :(得分：19)
需要一些改进，但是：StrictMath来救援！
你可以将后缀放在一个字符串或数组中，并根据功率或类似的东西来设置fetch'em
该部门也可以围绕权力进行管理，我认为几乎所有事情都与权力价值有关。
希望它有所帮助！
public static String formatValue(double value) {
int power;
String suffix = " kmbt";
String formattedNumber = "";
NumberFormat formatter = new DecimalFormat("#,###.#");
power = (int)StrictMath.log10(value);
value = value/(Math.pow(10,(power/3)*3));
formattedNumber=formatter.format(value);
formattedNumber = formattedNumber + suffix.charAt(power/3);
return formattedNumber.length()>4 ? formattedNumber.replaceAll("\\.[0-9]+", "") : formattedNumber;
}
输出：
999
1.2K
98K
911k
1.1米
11B
712B
34t
答案 4 :(得分：15)
此解决方案（this answer的扩展名）解决了上述问题。
import org.apache.commons.lang.math.NumberUtils;
import java.text.DecimalFormat;
import java.text.FieldPosition;
import java.text.Format;
import java.text.ParsePosition;
import java.util.regex.Pattern;
/**
* Converts a number to a string in <a href="http://en.wikipedia.org/wiki/Metric_prefix">metric prefix</a> format.
* For example, 7800000 will be formatted as '7.8M'. Numbers under 1000 will be unchanged. Refer to the tests for further examples.
*/
class RoundedMetricPrefixFormat extends Format {
private static final String[] METRIC_PREFIXES = new String[]{"", "k", "M", "G", "T"};
/**
* The maximum number of characters in the output, excluding the negative sign
*/
private static final Integer MAX_LENGTH = 4;
private static final Pattern TRAILING_DECIMAL_POINT = Pattern.compile("[0-9]+\\.[kMGT]");
private static final Pattern METRIC_PREFIXED_NUMBER = Pattern.compile("\\-?[0-9]+(\\.[0-9])?[kMGT]");
@Override
public StringBuffer format(Object obj, StringBuffer output, FieldPosition pos) {
Double number = Double.valueOf(obj.toString());
// if the number is negative, convert it to a positive number and add the minus sign to the output at the end
boolean isNegative = number < 0;
number = Math.abs(number);
String result = new DecimalFormat("##0E0").format(number);
Integer index = Character.getNumericValue(result.charAt(result.length() - 1)) / 3;
result = result.replaceAll("E[0-9]", METRIC_PREFIXES[index]);
while (result.length() > MAX_LENGTH || TRAILING_DECIMAL_POINT.matcher(result).matches()) {
int length = result.length();
result = result.substring(0, length - 2) + result.substring(length - 1);
}
return output.append(isNegative ? "-" + result : result);
}
/**
* Convert a String produced by <tt>format()</tt> back to a number. This will generally not restore
* the original number because <tt>format()</tt> is a lossy operation, e.g.
*
* <pre>
* {@code
* def formatter = new RoundedMetricPrefixFormat()
* Long number = 5821L
* String formattedNumber = formatter.format(number)
* assert formattedNumber == '5.8k'
*
* Long parsedNumber = formatter.parseObject(formattedNumber)
* assert parsedNumber == 5800
* assert parsedNumber != number
* }
* </pre>
*
* @param source a number that may have a metric prefix
* @param pos if parsing succeeds, this should be updated to the index after the last parsed character
* @return a Number if the the string is a number without a metric prefix, or a Long if it has a metric prefix
*/
@Override
public Object parseObject(String source, ParsePosition pos) {
if (NumberUtils.isNumber(source)) {
// if the value is a number (without a prefix) don't return it as a Long or we'll lose any decimals
pos.setIndex(source.length());
return toNumber(source);
} else if (METRIC_PREFIXED_NUMBER.matcher(source).matches()) {
boolean isNegative = source.charAt(0) == '-';
int length = source.length();
String number = isNegative ? source.substring(1, length - 1) : source.substring(0, length - 1);
String metricPrefix = Character.toString(source.charAt(length - 1));
Number absoluteNumber = toNumber(number);
int index = 0;
for (; index < METRIC_PREFIXES.length; index++) {
if (METRIC_PREFIXES[index].equals(metricPrefix)) {
break;
}
}
Integer exponent = 3 * index;
Double factor = Math.pow(10, exponent);
factor *= isNegative ? -1 : 1;
pos.setIndex(source.length());
Float result = absoluteNumber.floatValue() * factor.longValue();
return result.longValue();
}
return null;
}
private static Number toNumber(String number) {
return NumberUtils.createNumber(number);
}
}
该解决方案最初是用Groovy编写的，如下所示。
import org.apache.commons.lang.math.NumberUtils
import java.text.DecimalFormat
import java.text.FieldPosition
import java.text.Format
import java.text.ParsePosition
import java.util.regex.Pattern
/**
* Converts a number to a string in <a href="http://en.wikipedia.org/wiki/Metric_prefix">metric prefix</a> format.
* For example, 7800000 will be formatted as '7.8M'. Numbers under 1000 will be unchanged. Refer to the tests for further examples.
*/
class RoundedMetricPrefixFormat extends Format {
private static final METRIC_PREFIXES = ["", "k", "M", "G", "T"]
/**
* The maximum number of characters in the output, excluding the negative sign
*/
private static final Integer MAX_LENGTH = 4
private static final Pattern TRAILING_DECIMAL_POINT = ~/[0-9]+\.[kMGT]/
private static final Pattern METRIC_PREFIXED_NUMBER = ~/\-?[0-9]+(\.[0-9])?[kMGT]/
@Override
StringBuffer format(Object obj, StringBuffer output, FieldPosition pos) {
Double number = obj as Double
// if the number is negative, convert it to a positive number and add the minus sign to the output at the end
boolean isNegative = number < 0
number = Math.abs(number)
String result = new DecimalFormat("##0E0").format(number)
Integer index = Character.getNumericValue(result.charAt(result.size() - 1)) / 3
result = result.replaceAll("E[0-9]", METRIC_PREFIXES[index])
while (result.size() > MAX_LENGTH || TRAILING_DECIMAL_POINT.matcher(result).matches()) {
int length = result.size()
result = result.substring(0, length - 2) + result.substring(length - 1)
}
output << (isNegative ? "-$result" : result)
}
/**
* Convert a String produced by <tt>format()</tt> back to a number. This will generally not restore
* the original number because <tt>format()</tt> is a lossy operation, e.g.
*
* <pre>
* {@code
* def formatter = new RoundedMetricPrefixFormat()
* Long number = 5821L
* String formattedNumber = formatter.format(number)
* assert formattedNumber == '5.8k'
*
* Long parsedNumber = formatter.parseObject(formattedNumber)
* assert parsedNumber == 5800
* assert parsedNumber != number
* }
* </pre>
*
* @param source a number that may have a metric prefix
* @param pos if parsing succeeds, this should be updated to the index after the last parsed character
* @return a Number if the the string is a number without a metric prefix, or a Long if it has a metric prefix
*/
@Override
Object parseObject(String source, ParsePosition pos) {
if (source.isNumber()) {
// if the value is a number (without a prefix) don't return it as a Long or we'll lose any decimals
pos.index = source.size()
toNumber(source)
} else if (METRIC_PREFIXED_NUMBER.matcher(source).matches()) {
boolean isNegative = source[0] == '-'
String number = isNegative ? source[1..-2] : source[0..-2]
String metricPrefix = source[-1]
Number absoluteNumber = toNumber(number)
Integer exponent = 3 * METRIC_PREFIXES.indexOf(metricPrefix)
Long factor = 10 ** exponent
factor *= isNegative ? -1 : 1
pos.index = source.size()
(absoluteNumber * factor) as Long
}
}
private static Number toNumber(String number) {
NumberUtils.createNumber(number)
}
}
测试是用Groovy编写的，但可用于验证Java或Groovy类（因为它们都具有相同的名称和API）。
import java.text.Format
import java.text.ParseException
class RoundedMetricPrefixFormatTests extends GroovyTestCase {
private Format roundedMetricPrefixFormat = new RoundedMetricPrefixFormat()
void testNumberFormatting() {
[
7L : '7',
12L : '12',
856L : '856',
1000L : '1k',
(-1000L) : '-1k',
5821L : '5.8k',
10500L : '10k',
101800L : '102k',
2000000L : '2M',
7800000L : '7.8M',
(-7800000L): '-7.8M',
92150000L : '92M',
123200000L : '123M',
9999999L : '10M',
(-9999999L): '-10M'
].each { Long rawValue, String expectedRoundValue ->
assertEquals expectedRoundValue, roundedMetricPrefixFormat.format(rawValue)
}
}
void testStringParsingSuccess() {
[
'7' : 7,
'8.2' : 8.2F,
'856' : 856,
'-856' : -856,
'1k' : 1000,
'5.8k' : 5800,
'-5.8k': -5800,
'10k' : 10000,
'102k' : 102000,
'2M' : 2000000,
'7.8M' : 7800000L,
'92M' : 92000000L,
'-92M' : -92000000L,
'123M' : 123000000L,
'10M' : 10000000L
].each { String metricPrefixNumber, Number expectedValue ->
def parsedNumber = roundedMetricPrefixFormat.parseObject(metricPrefixNumber)
assertEquals expectedValue, parsedNumber
}
}
void testStringParsingFail() {
shouldFail(ParseException) {
roundedMetricPrefixFormat.parseObject('notNumber')
}
}
}
答案 5 :(得分：9)
ICU lib有一个基于规则的数字格式化程序，可用于数字拼写等。我认为使用ICU会为您提供可读且可维护的解决方案。
<强> [使用方法]
正确的类是RuleBasedNumberFormat。格式本身可以存储为单独的文件（或String常量，IIRC）。
来自http://userguide.icu-project.org/formatparse/numbers
的示例double num = 2718.28;
NumberFormat formatter =
new RuleBasedNumberFormat(RuleBasedNumberFormat.SPELLOUT);
String result = formatter.format(num);
System.out.println(result);
同一页面显示罗马数字，所以我想你的情况也应该是可能的。
答案 6 :(得分：7)
对于任何想要回合的人。这是一个很好的，易于阅读的解决方案，它利用了Java.Lang.Math库
public static String formatNumberExample(Number number) {
char[] suffix = {' ', 'k', 'M', 'B', 'T', 'P', 'E'};
long numValue = number.longValue();
int value = (int) Math.floor(Math.log10(numValue));
int base = value / 3;
if (value >= 3 && base < suffix.length) {
return new DecimalFormat("~#0.0").format(numValue / Math.pow(10, base * 3)) + suffix[base];
} else {
return new DecimalFormat("#,##0").format(numValue);
}
}
答案 7 :(得分：7)
重要提示：对double之类的数字投降99999999999999999L的答案将失败并返回100P而不是99P，因为double使用IEEE standard：
如果最多15位有效数字的十进制字符串转换为IEEE 754双精度表示形式，然后转换回具有相同有效位数的字符串，则最终字符串应与原版的。 [
long最多19个有效数字。]
System.out.println((long)(double)99999999999999992L); // 100000000000000000
System.out.println((long)(double)99999999999999991L); // 99999999999999984
// it is even worse for the logarithm:
System.out.println(Math.log10(99999999999999600L)); // 17.0
System.out.println(Math.log10(99999999999999500L)); // 16.999999999999996
此解决方案可以切断不需要的数字，适用于所有long值。简单但高性能的实现（下面的比较）。 -120k不能用4个字符表示，即使-0.1M太长，这就是为什么负数5个字符必须是好的：
private static final char[] magnitudes = {'k', 'M', 'G', 'T', 'P', 'E'}; // enough for long
public static final String convert(long number) {
String ret;
if (number >= 0) {
ret = "";
} else if (number <= -9200000000000000000L) {
return "-9.2E";
} else {
ret = "-";
number = -number;
}
if (number < 1000)
return ret + number;
for (int i = 0; ; i++) {
if (number < 10000 && number % 1000 >= 100)
return ret + (number / 1000) + '.' + ((number % 1000) / 100) + magnitudes[i];
number /= 1000;
if (number < 1000)
return ret + number + magnitudes[i];
}
}
开头else if中的测试是必要的，因为最小值为-(2^63)，最大值为(2^63)-1，因此如果{{1}，则分配number = -number将失败}}。如果我们必须进行检查，那么我们也可以包含尽可能多的数字，而不仅仅是检查number == Long.MIN_VALUE。
将此实施方案与获得最多投票权的人（当前表示最快）进行比较，结果表明 <5>快（取决于测试设置，但是更多的数字，增益变得更大，这个实现必须做更多的检查，因为它处理所有情况，所以如果另一个将被修复，差异将变得更大）。它是快速的，因为没有浮点运算，没有对数，没有幂，没有递归，没有正则表达式，没有复杂的格式化程序和最小化创建的对象数量。
以下是测试程序：
number == Long.MIN_VALUE可能的输出：public class Test {
public static void main(String[] args) {
long[] numbers = new long[20000000];
for (int i = 0; i < numbers.length; i++)
numbers[i] = Math.random() < 0.5 ? (long) (Math.random() * Long.MAX_VALUE) : (long) (Math.random() * Long.MIN_VALUE);
System.out.println(convert1(numbers) + " vs. " + convert2(numbers));
}
private static long convert1(long[] numbers) {
long l = System.currentTimeMillis();
for (int i = 0; i < numbers.length; i++)
Converter1.convert(numbers[i]);
return System.currentTimeMillis() - l;
}
private static long convert2(long[] numbers) {
long l = System.currentTimeMillis();
for (int i = 0; i < numbers.length; i++)
Converter2.coolFormat(numbers[i], 0);
return System.currentTimeMillis() - l;
}
}
（当只使用正数时大致相同，而在颠倒执行顺序时更为极端，可能与垃圾收集有关）
答案 8 :(得分：7)
这是一个没有递归的简短实现，只是一个非常小的循环。不适用于负数但支持所有正long以及Long.MAX_VALUE：
private static final char[] SUFFIXES = {'k', 'm', 'g', 't', 'p', 'e' };
public static String format(long number) {
if(number < 1000) {
// No need to format this
return String.valueOf(number);
}
// Convert to a string
final String string = String.valueOf(number);
// The suffix we're using, 1-based
final int magnitude = (string.length() - 1) / 3;
// The number of digits we must show before the prefix
final int digits = (string.length() - 1) % 3 + 1;
// Build the string
char[] value = new char[4];
for(int i = 0; i < digits; i++) {
value[i] = string.charAt(i);
}
int valueLength = digits;
// Can and should we add a decimal point and an additional number?
if(digits == 1 && string.charAt(1) != '0') {
value[valueLength++] = '.';
value[valueLength++] = string.charAt(1);
}
value[valueLength++] = SUFFIXES[magnitude - 1];
return new String(value, 0, valueLength);
}
输出：
1K
5.8K
10K
101K
2米
7.8米
92米
123米
9.2e（这是Long.MAX_VALUE）
我还做了一些非常简单的基准测试（格式化1000万随机长片），它比Elijah的实现快得多，并且比assylias的实现快一点。
我的：1137.028毫秒 以利亚的：2664.396 ms
assylias'：1373.473 ms
答案 9 :(得分：6)
我不知道这是不是最好的方法，但这就是我所做的。
7=>7
12=>12
856=>856
1000=>1.0k
5821=>5.82k
10500=>10.5k
101800=>101.8k
2000000=>2.0m
7800000=>7.8m
92150000=>92.15m
123200000=>123.2m
9999999=>10.0m
---代码---
public String Format(Integer number){
String[] suffix = new String[]{"k","m","b","t"};
int size = (number.intValue() != 0) ? (int) Math.log10(number) : 0;
if (size >= 3){
while (size % 3 != 0) {
size = size - 1;
}
}
double notation = Math.pow(10, size);
String result = (size >= 3) ? + (Math.round((number / notation) * 100) / 100.0d)+suffix[(size/3) - 1] : + number + "";
return result
}
答案 10 :(得分：6)
以下代码说明了如何通过轻松扩展来实现这一目标。
“魔法”主要存在于makeDecimal函数中，对于传入的正确值，它保证输出中永远不会有超过四个字符。
它首先提取给定除数的整数和十分之一部分，例如，12,345,678除数为1,000,000，whole值为12且tenths值为3。
从那以后，它可以决定是使用规则输出整个部分还是整个部分和十分之一部分：
以下代码：
static private String makeDecimal(long val, long div, String sfx) {
val = val / (div / 10);
long whole = val / 10;
long tenths = val % 10;
if ((tenths == 0) || (whole >= 10))
return String.format("%d%s", whole, sfx);
return String.format("%d.%d%s", whole, tenths, sfx);
}
然后，使用正确的值调用辅助函数是一件简单的事情，包括一些使开发人员更容易生活的常量：
static final long THOU = 1000L;
static final long MILL = 1000000L;
static final long BILL = 1000000000L;
static final long TRIL = 1000000000000L;
static final long QUAD = 1000000000000000L;
static final long QUIN = 1000000000000000000L;
static private String Xlat(long val) {
if (val < THOU) return Long.toString(val);
if (val < MILL) return makeDecimal(val, THOU, "k");
if (val < BILL) return makeDecimal(val, MILL, "m");
if (val < TRIL) return makeDecimal(val, BILL, "b");
if (val < QUAD) return makeDecimal(val, TRIL, "t");
if (val < QUIN) return makeDecimal(val, QUAD, "q");
return makeDecimal(val, QUIN, "u");
}
makeDecimal函数执行繁琐的工作这一事实意味着扩展到999,999,999之后只需向Xlat添加额外的一行，我就这么简单了对你而言。
return中的最终Xlat不需要条件，因为在64位有符号长整数中，您可以保留的最大值仅为9.2 quintillion。
但是，如果根据某些奇怪的要求，Oracle决定添加128位longer类型或1024位damn_long类型，那么您将为此做好准备： - ）
最后，您可以使用一些测试工具来验证功能。
public static void main(String[] args) {
long vals[] = {
999L, 1000L, 5821L, 10500L, 101800L, 2000000L,
7800000L, 92150000L, 123200000L, 999999999L,
1000000000L, 1100000000L, 999999999999L,
1000000000000L, 999999999999999L,
1000000000000000L, 9223372036854775807L
};
for (long val: vals)
System.out.println ("" + val + " -> " + Xlat(val));
}
}
您可以从输出中看到它可以满足您的需求：
999 -> 999
1000 -> 1k
5821 -> 5.8k
10500 -> 10k
101800 -> 101k
2000000 -> 2m
7800000 -> 7.8m
92150000 -> 92m
123200000 -> 123m
999999999 -> 999m
1000000000 -> 1b
1100000000 -> 1.1b
999999999999 -> 999b
1000000000000 -> 1t
999999999999999 -> 999t
1000000000000000 -> 1q
9223372036854775807 -> 9.2u
另外，请注意，将负数传递给此函数会导致字符串太长而无法满足您的要求，因为它遵循
< THOU路径）。我认为这很好，因为你只在问题中提到了非负值。
答案 11 :(得分：5)
我的最爱。您可以使用“k”等作为十进制的指示符，这在电子域中很常见。这将为您提供额外的数字，而无需额外的空间
第二列尝试使用尽可能多的数字
1000 => 1.0k | 1000
5821 => 5.8k | 5821
10500 => 10k | 10k5
101800 => 101k | 101k
2000000 => 2.0m | 2m
7800000 => 7.8m | 7m8
92150000 => 92m | 92m1
123200000 => 123m | 123m
9999999 => 9.9m | 9m99
这是代码
public class HTTest {
private static String[] unit = {"u", "k", "m", "g", "t"};
/**
* @param args
*/
public static void main(String[] args) {
int[] numbers = new int[]{1000, 5821, 10500, 101800, 2000000, 7800000, 92150000, 123200000, 9999999};
for(int n : numbers) {
System.out.println(n + " => " + myFormat(n) + " | " + myFormat2(n));
}
}
private static String myFormat(int pN) {
String str = Integer.toString(pN);
int len = str.length ()-1;
if (len <= 3) return str;
int level = len / 3;
int mode = len % 3;
switch (mode) {
case 0: return str.substring(0, 1) + "." + str.substring(1, 2) + unit[level];
case 1: return str.substring(0, 2) + unit[level];
case 2: return str.substring(0, 3) + unit[level];
}
return "how that?";
}
private static String trim1 (String pVal) {
if (pVal.equals("0")) return "";
return pVal;
}
private static String trim2 (String pVal) {
if (pVal.equals("00")) return "";
return pVal.substring(0, 1) + trim1(pVal.substring(1,2));
}
private static String myFormat2(int pN) {
String str = Integer.toString(pN);
int len = str.length () - 1;
if (len <= 3) return str;
int level = len / 3;
int mode = len % 3;
switch (mode) {
case 0: return str.substring(0, 1) + unit[level] + trim2(str.substring(1, 3));
case 2: return str.substring(0, 3) + unit[level];
case 1: return str.substring(0, 2) + unit[level] + trim1(str.substring(2, 3));
}
return "how that?";
}
}
答案 12 :(得分：5)
使用 JDK / 12 build：26 ，您现在可以使用https://myWSdomain.mydomain.com设置数字格式。您可以先创建一个restTemplate.setInterceptors(Collections.singletonList(new RestInterceptor ()));
作为
NumberFormat，然后将其用于NumberFormat fmt = NumberFormat.getCompactNumberInstance(Locale.US, NumberFormat.Style.SHORT);
，
format
答案 13 :(得分：5)
我的Java生疏了，但这是我在C＃中实现它的方式：
private string FormatNumber(double value)
{
string[] suffixes = new string[] {" k", " m", " b", " t", " q"};
for (int j = suffixes.Length; j > 0; j--)
{
double unit = Math.Pow(1000, j);
if (value >= unit)
return (value / unit).ToString("#,##0.0") + suffixes[--j];
}
return value.ToString("#,##0");
}
很容易将其调整为使用CS公斤（1,024）而不是公制公斤，或者添加更多单位。它将1,000格式化为“1.0 k”而不是“1 k”，但我相信这是无关紧要的。
为了满足更具体的要求“不超过四个字符”，删除后缀之前的空格并调整中间块，如下所示：
if (value >= unit)
{
value /= unit;
return (value).ToString(value >= unit * 9.95 ? "#,##0" : "#,##0.0") + suffixes[--j];
}
答案 14 :(得分：4)
坚持我的评论，我认为可读性高于性能，这是一个应该清楚发生了什么的版本（假设你之前已经使用过BigDecimal）没有过多的评论（我相信自我 - 记录代码），而不用担心性能（因为我无法想象你想要做到这么多次的情况，性能甚至成为一个考虑因素）。
此版本：
BigDecimal来提高精确度并避免舍入问题HALF_UP）REQUIRED_PRECISION来定义阈值，即可以轻松调整为使用KB / MB / GB / TB而不是k / m / b / t等，当然可以扩展到{ {1}}如果需要<强> Threshold.java ：
enum<强> NumberShortener.java ：
TRILLION（取消注释import java.math.BigDecimal;
public enum Threshold {
TRILLION("1000000000000", 12, 't', null),
BILLION("1000000000", 9, 'b', TRILLION),
MILLION("1000000", 6, 'm', BILLION),
THOUSAND("1000", 3, 'k', MILLION),
ZERO("0", 0, null, THOUSAND);
private BigDecimal value;
private int zeroes;
protected Character suffix;
private Threshold higherThreshold;
private Threshold(String aValueString, int aNumberOfZeroes, Character aSuffix,
Threshold aThreshold) {
value = new BigDecimal(aValueString);
zeroes = aNumberOfZeroes;
suffix = aSuffix;
higherThreshold = aThreshold;
}
public static Threshold thresholdFor(long aValue) {
return thresholdFor(new BigDecimal(aValue));
}
public static Threshold thresholdFor(BigDecimal aValue) {
for (Threshold eachThreshold : Threshold.values()) {
if (eachThreshold.value.compareTo(aValue) <= 0) {
return eachThreshold;
}
}
return TRILLION; // shouldn't be needed, but you might have to extend the enum
}
public int getNumberOfZeroes() {
return zeroes;
}
public String getSuffix() {
return suffix == null ? "" : "" + suffix;
}
public Threshold getHigherThreshold() {
return higherThreshold;
}
}
语句或更改为使用您最喜爱的记录器来查看它正在做什么。）
最后， NumberShortenerTest （普通JUnit 4）中的测试：
import java.math.BigDecimal;
import java.math.RoundingMode;
public class NumberShortener {
public static final int REQUIRED_PRECISION = 2;
public static BigDecimal toPrecisionWithoutLoss(BigDecimal aBigDecimal,
int aPrecision, RoundingMode aMode) {
int previousScale = aBigDecimal.scale();
int previousPrecision = aBigDecimal.precision();
int newPrecision = Math.max(previousPrecision - previousScale, aPrecision);
return aBigDecimal.setScale(previousScale + newPrecision - previousPrecision,
aMode);
}
private static BigDecimal scaledNumber(BigDecimal aNumber, RoundingMode aMode) {
Threshold threshold = Threshold.thresholdFor(aNumber);
BigDecimal adjustedNumber = aNumber.movePointLeft(threshold.getNumberOfZeroes());
BigDecimal scaledNumber = toPrecisionWithoutLoss(adjustedNumber, REQUIRED_PRECISION,
aMode).stripTrailingZeros();
// System.out.println("Number: <" + aNumber + ">, adjusted: <" + adjustedNumber
// + ">, rounded: <" + scaledNumber + ">");
return scaledNumber;
}
public static String shortenedNumber(long aNumber, RoundingMode aMode) {
boolean isNegative = aNumber < 0;
BigDecimal numberAsBigDecimal = new BigDecimal(isNegative ? -aNumber : aNumber);
Threshold threshold = Threshold.thresholdFor(numberAsBigDecimal);
BigDecimal scaledNumber = aNumber == 0 ? numberAsBigDecimal : scaledNumber(
numberAsBigDecimal, aMode);
if (scaledNumber.compareTo(new BigDecimal("1000")) >= 0) {
scaledNumber = scaledNumber(scaledNumber, aMode);
threshold = threshold.getHigherThreshold();
}
String sign = isNegative ? "-" : "";
String printNumber = sign + scaledNumber.stripTrailingZeros().toPlainString()
+ threshold.getSuffix();
// System.out.println("Number: <" + sign + numberAsBigDecimal + ">, rounded: <"
// + sign + scaledNumber + ">, print: <" + printNumber + ">");
return printNumber;
}
}
如果我错过了一个重要的测试用例或者是否应该调整预期值，请随意在评论中指出。
答案 15 :(得分：2)
添加我自己的答案，Java代码，自解释代码..
import java.math.BigDecimal;
/**
* Method to convert number to formatted number.
*
* @author Gautham PJ
*/
public class ShortFormatNumbers
{
/**
* Main method. Execution starts here.
*/
public static void main(String[] args)
{
// The numbers that are being converted.
int[] numbers = {999, 1400, 2500, 45673463, 983456, 234234567};
// Call the "formatNumber" method on individual numbers to format
// the number.
for(int number : numbers)
{
System.out.println(number + ": " + formatNumber(number));
}
}
/**
* Format the number to display it in short format.
*
* The number is divided by 1000 to find which denomination to be added
* to the number. Dividing the number will give the smallest possible
* value with the denomination.
*
* @param the number that needs to be converted to short hand notation.
* @return the converted short hand notation for the number.
*/
private static String formatNumber(double number)
{
String[] denominations = {"", "k", "m", "b", "t"};
int denominationIndex = 0;
// If number is greater than 1000, divide the number by 1000 and
// increment the index for the denomination.
while(number > 1000.0)
{
denominationIndex++;
number = number / 1000.0;
}
// To round it to 2 digits.
BigDecimal bigDecimal = new BigDecimal(number);
bigDecimal = bigDecimal.setScale(2, BigDecimal.ROUND_HALF_EVEN);
// Add the number with the denomination to get the final value.
String formattedNumber = bigDecimal + denominations[denominationIndex];
return formattedNumber;
}
}
答案 16 :(得分：2)
我将大数字转换为小数字（2位数字）的功能。您可以通过更改#.##
DecimalFormat来更改位数
public String formatValue(float value) {
String arr[] = {"", "K", "M", "B", "T", "P", "E"};
int index = 0;
while ((value / 1000) >= 1) {
value = value / 1000;
index++;
}
DecimalFormat decimalFormat = new DecimalFormat("#.##");
return String.format("%s %s", decimalFormat.format(value), arr[index]);
}
测试
System.out.println(formatValue(100)); // 100
System.out.println(formatValue(1000)); // 1 K
System.out.println(formatValue(10345)); // 10.35 K
System.out.println(formatValue(10012)); // 10.01 K
System.out.println(formatValue(123456)); // 123.46 K
System.out.println(formatValue(4384324)); // 4.38 M
System.out.println(formatValue(10000000)); // 10 M
System.out.println(formatValue(Long.MAX_VALUE)); // 9.22 E
希望有帮助
答案 17 :(得分：1)
此代码段只是致命的简单，干净的代码，完全有效：
private static char[] c = new char[]{'K', 'M', 'B', 'T'};
private String formatK(double n, int iteration) {
if (n < 1000) {
// print 999 or 999K
if (iteration <= 0) {
return String.valueOf((long) n);
} else {
return String.format("%d%s", Math.round(n), c[iteration-1]);
}
} else if (n < 10000) {
// Print 9.9K
return String.format("%.1f%s", n/1000, c[iteration]);
} else {
// Increase 1 iteration
return formatK(Math.round(n/1000), iteration+1);
}
}
答案 18 :(得分：1)
试试这个：
public String Format(Integer number){
String[] suffix = new String[]{"k","m","b","t"};
int size = (number.intValue() != 0) ? (int) Math.log10(number) : 0;
if (size >= 3){
while (size % 3 != 0) {
size = size - 1;
}
}
double notation = Math.pow(10, size);
String result = (size >= 3) ? + (Math.round((number / notation) * 100) / 100.0d)+suffix[(size/3) - 1] : + number + "";
return result
}
答案 19 :(得分：1)
这是我的代码。干净简单。
public static String getRoughNumber(long value) {
if (value <= 999) {
return String.valueOf(value);
}
final String[] units = new String[]{"", "K", "M", "B", "P"};
int digitGroups = (int) (Math.log10(value) / Math.log10(1000));
return new DecimalFormat("#,##0.#").format(value / Math.pow(1000, digitGroups)) + "" + units[digitGroups];
}
答案 20 :(得分：1)
Maven Central 上有解决方案
<dependency>
<groupId>com.github.bogdanovmn.humanreadablevalues</groupId>
<artifactId>human-readable-values</artifactId>
<version>1.0.1</version>
</dependency>
您可以只获取字节数或秒数的值。您也可以创建自己的分解类。
文档 https://github.com/bogdanovmn/java-human-readable-values
秒示例
assertEquals(
"2h 46m 40s",
new SecondsValue(10000).fullString()
);
assertEquals(
"2.8h",
new SecondsValue(10000).shortString()
);
字节示例
assertEquals(
"9K 784b",
new BytesValue(10000).fullString()
);
assertEquals(
"9.8K",
new BytesValue(10000).shortString()
);
答案 21 :(得分：0)
//code longer but work sure...
public static String formatK(int number) {
if (number < 999) {
return String.valueOf(number);
}
if (number < 9999) {
String strNumber = String.valueOf(number);
String str1 = strNumber.substring(0, 1);
String str2 = strNumber.substring(1, 2);
if (str2.equals("0")) {
return str1 + "k";
} else {
return str1 + "." + str2 + "k";
}
}
if (number < 99999) {
String strNumber = String.valueOf(number);
String str1 = strNumber.substring(0, 2);
return str1 + "k";
}
if (number < 999999) {
String strNumber = String.valueOf(number);
String str1 = strNumber.substring(0, 3);
return str1 + "k";
}
if (number < 9999999) {
String strNumber = String.valueOf(number);
String str1 = strNumber.substring(0, 1);
String str2 = strNumber.substring(1, 2);
if (str2.equals("0")) {
return str1 + "m";
} else {
return str1 + "." + str2 + "m";
}
}
if (number < 99999999) {
String strNumber = String.valueOf(number);
String str1 = strNumber.substring(0, 2);
return str1 + "m";
}
if (number < 999999999) {
String strNumber = String.valueOf(number);
String str1 = strNumber.substring(0, 3);
return str1 + "m";
}
NumberFormat formatterHasDigi = new DecimalFormat("###,###,###");
return formatterHasDigi.format(number);
}
答案 22 :(得分：0)
public class NumberToReadableWordFormat {
public static void main(String[] args) {
Integer[] numbers = new Integer[]{1000, 5821, 10500, 101800, 2000000, 7800000, 92150000, 123200000, 9999999,999};
for(int n : numbers) {
System.out.println(n + " => " + coolFormat(n));
}
}
private static String[] c = new String[]{"K", "L", "Cr"};
private static String coolFormat(int n) {
int size = String.valueOf(n).length();
if (size>=4 && size<6) {
int value = (int) Math.pow(10, 1);
double d = (double) Math.round(n/1000.0 * value) / value;
return (double) Math.round(n/1000.0 * value) / value+" "+c[0];
} else if(size>5 && size<8) {
int value = (int) Math.pow(10, 1);
return (double) Math.round(n/100000.0 * value) / value+" "+c[1];
} else if(size>=8) {
int value = (int) Math.pow(10, 1);
return (double) Math.round(n/10000000.0 * value) / value+" "+c[2];
} else {
return n+"";
}
}
}
输出：
1000 => 1.0 K
5821 => 5.8 K
10500 => 10.5 K
101800 => 1.0 L
2000000 => 20.0 L
7800000 => 78.0 L
92150000 => 9.2 Cr
123200000 => 12.3 Cr
9999999 => 100.0 L
999 => 999
答案 23 :(得分：0)
这是您问题的另一种简单解决方案。 说
String abbr="M,K,T,B";
double yvalue =一些随机数； String string =“＃。##” //任意位置的小数位
public String format(Double yvalue, String string,String abbr) {
DecimalFormat df = new DecimalFormat(getnumberformatpattern(string));
if (yvalue < 0) return "-" + format(-yvalue,string,abbr);
double finalvalue= yvalue;
String newnumber="";
if (abbr.indexOf("K")>0){
finalvalue= (yvalue / 1e3);
newnumber=df.format(finalvalue) +'K';
}
if (abbr.indexOf("M")>0 ){
if(yvalue>=1e6){
finalvalue= (yvalue / 1e6);
newnumber=df.format(finalvalue) +'M';
};
}
if (abbr.indexOf("B")>0 )
{
if((newnumber.indexOf("M")<0) || yvalue>=1e9){
finalvalue= (yvalue / 1e9);
newnumber=df.format(finalvalue) +'B'; }
}
if (abbr.indexOf("T")>0 ){
if((newnumber.indexOf("B")<0) || yvalue>=1e12){
finalvalue= (yvalue / 1e12);
newnumber=df.format(finalvalue) +'T'; }
}
return newnumber;
}
答案 24 :(得分：0)
根据输入的数字设置除数：1000、100000、1000000、1000000000等...
检查数字的整个部分（没有小数的第一部分），如果其大小为 1，然后将输入转换为 long + String。 如果大小 >= 2，则除以输入并使用 DecimalFormat 根据需要显示小数部分。
可以使用 // .setRoundingMode(RoundingMode.DOWN) 来处理舍入
public static String format(long num) {
String suffix = "", result;
double divisor = 0;
DecimalFormat df = new DecimalFormat("##");
DecimalFormat ds = new DecimalFormat("##.#");
// ds.setRoundingMode(RoundingMode.DOWN);
if ( num >= 1000 && num < 1000000 ) {
divisor = 1000;
suffix = "K";
} else if ( num >= 1000000 && num < 1000000000 ) {
divisor = 1000000;
suffix = "M";
} else if (num >= 1000000000) {
divisor = 1000000000;
suffix = "B";
} else {
System.out.print("The number is Too big > T or TOO small < K");
}
int numlengt = df.format(num / divisor).length();
if (numlengt >= 2) {
result = (long) (num / divisor) + suffix;
} else {
result = ds.format(num / divisor) + suffix;
}
return result;
}