How to nicely format floating numbers to string without unnecessary decimal 0 s

Question

A 64-bit double can represent integer   - 253 exactly  Given this fact  I choose to use a double type as a single type for all my types  since my largest integer is an unsigned 32-bit number  But now I have to print these pseudo integers  but the problem is they are also mixed in with actual doubles  So how do I print these doubles nicely in Java  I have tried String format  quot  f quot   value   which is close  except I get a lot of trailing zeros for small values  Here s an example output of of  f  232 00000000 0 18000000000 1237875192 0 4 5800000000 0 00000000 1 23450000  What I want is   232 0 18 1237875192 4 58 0 1 2345  Sure I can write a function to trim those zeros  but that s lot of performance loss due to string manipulation  Can I do better with other format code   The answers by Tom E  and Jeremy S  are unacceptable as they both arbitrarily rounds to two decimal places  Please understand the problem before answering   Please note that String format format  args     is locale-dependent  see answers below

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float price   4 30  DecimalFormat format   new DecimalFormat  quot 0    quot       Choose the number of decimal places to work with in case they are different than zero and zero value will be removed format setRoundingMode RoundingMode DOWN      Choose your Rounding Mode System out println format format price     This is the result of some tests  4 30       gt  4 3 4 39       gt  4 39     Choose format setRoundingMode RoundingMode UP  to get 4 4 4 000000   gt  4 4          gt  4

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I am using this for formatting numbers without trailing zeroes in our JSF application  The original built-in formatters required you to specify max numbers of fractional digits which could be useful here also in case you have too many fractional digits         Formats the given Number as with as many fractional digits as precision    available  lt br gt     This is a convenient method in case all fractional digits shall be    rendered and no custom format   pattern needs to be provided  lt br gt      lt br gt     This serves as a workaround for   link NumberFormat getNumberInstance       which by default only renders up to three fractional digits         param number     param locale     param groupingUsed  lt code gt true lt  code gt  if grouping shall be used        return     public static String formatNumberFraction final Number number  final Locale locale  final boolean groupingUsed        if  number    null          return null       final BigDecimal bDNumber   MathUtils getBigDecimal number        final NumberFormat numberFormat   NumberFormat getNumberInstance locale       numberFormat setMaximumFractionDigits Math max 0  bDNumber scale          numberFormat setGroupingUsed groupingUsed           Convert back for locale percent formatter     return numberFormat format bDNumber             Formats the given Number as percent with as many fractional digits as    precision available  lt br gt     This is a convenient method in case all fractional digits shall be    rendered and no custom format   pattern needs to be provided  lt br gt      lt br gt     This serves as a workaround for   link NumberFormat getPercentInstance       which does not renders fractional digits         param number Number in range of  0-1      param locale        return     public static String formatPercentFraction final Number number  final Locale locale        if  number    null          return null       final BigDecimal bDNumber   MathUtils getBigDecimal number  multiply new BigDecimal 100         final NumberFormat percentScaleFormat   NumberFormat getPercentInstance locale       percentScaleFormat setMaximumFractionDigits Math max 0  bDNumber scale   - 2         final BigDecimal bDNumberPercent   bDNumber multiply new BigDecimal 0 01            Convert back for locale percent formatter     final String strPercent   percentScaleFormat format bDNumberPercent        return strPercent

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My two cents  if n   1    0        return String format Locale US   quot   0f quot   n      else       return String format Locale US   quot   1f quot   n

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This one will gets the job done nicely      public static String removeZero double number            DecimalFormat format   new DecimalFormat  quot               quot            return format format number

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For Kotlin you can use an extension like  fun Double toPrettyString         if this - this toLong      0 0          String format  quot  d quot   this toLong        else         String format  quot  s quot   this

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String format  quot   2f quot   value

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public static String fmt double d        String val   Double toString d       String   valArray   val split  quot     quot        long valLong   0      if valArray length    2            valLong   Long parseLong valArray 1               if  valLong    0          return String format  quot  d quot    long  d       else         return String format  quot  s quot   d      I had to use this because d     long d was giving me violation in a SonarQube report

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Here s another answer that has an option to append decimal ONLY IF decimal was not zero                 Example   isDecimalRequired   true         d   12345        returns 12 345 00               d   12345 12345        returns 12 345 12                                                                         Example   isDecimalRequired   false         d   12345        returns 12 345  notice that there s no decimal since it s zero                d   12345 12345        returns 12 345 12                param d float to format         param zeroCount number decimal places         param isDecimalRequired true if it will put decimal even zero         false will remove the last decimal s  if zero              fun formatDecimal d  Float    0f  zeroCount  Int  isDecimalRequired  Boolean   true   String           val zeros   StringBuilder            for  i in 0 until zeroCount                zeros append  0                      var pattern        0           if  zeros isNotEmpty                  pattern       zeros                     val numberFormat   DecimalFormat pattern           var formattedNumber   if  d    null  numberFormat format d  else  0           if   isDecimalRequired                for  i in formattedNumber length downTo formattedNumber length - zeroCount                    val number   formattedNumber i - 1                   if  number     0     number                               formattedNumber   formattedNumber substring 0  formattedNumber length - 1                    else                       break                                                    return formattedNumber

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Here are two ways to achieve it  First  the shorter  and probably better  way  public static String formatFloatToString final float f      final int i    int f    if f    i      return Integer toString i     return Float toString f      And here s the longer and probably worse way  public static String formatFloatToString final float f      final String s   Float toString f     int dotPos   -1    for int i 0  i lt s length      i      if s charAt i                      dotPos   i        break           if dotPos    -1      return s     int end   dotPos    for int i   dotPos   1  i lt s length      i          final char c   s charAt i       if c     0         end   i   1        final String result   s substring 0  end     return result

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Naw  never mind  The performance loss due to string manipulation is zero  And here s the code to trim the end after  f  private static String trimTrailingZeros String number        if  number contains  quot   quot              return number             return number replaceAll  quot     0   quot    quot  quot

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The best way to do this is as below  public class Test        public static void main String args             System out println String format  quot  s something quot   new Double 3 456             System out println String format  quot  s something quot   new Double 3 456234523452             System out println String format  quot  s something quot   new Double 3 45             System out println String format  quot  s something quot   new Double 3              Output  3 456 something 3 456234523452 something 3 45 something 3 0 something  The only issue is the last one where  0 doesn t get removed  But if you are able to live with that then this works best    2f will round it to the last two decimal digits  So will DecimalFormat  If you need all the decimal places  but not the trailing zeros then this works best

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On my machine  the following function is roughly 7 times faster than the function provided by JasonD s answer  since it avoids String format   public static String prettyPrint double d      int i    int  d    return d    i   String valueOf i    String valueOf d

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Please note that String format format  args     is locale-dependent because it formats using the user s default locale  that is  probably with commas and even spaces inside like 123 456 789 or 123 456 789  which may be not exactly what you expect   You may prefer to use String format  Locale null  format  args       For example       double f   123456 789d      System out println String format Locale FRANCE   f  f        System out println String format Locale GERMANY   f  f        System out println String format Locale US   f  f      prints  123456 789000 123456 789000 123456 789000   and this is what will String format format  args     do in different countries   EDIT Ok  since there has been a discussion about formalities       res    stripFpZeroes String format  Locale  null   nDigits  0        nDigits  f      f    value             protected static String stripFpZeroes String fpnumber        int n   fpnumber indexOf           if  n    -1            return fpnumber            if  n  lt  2            n   2            String s   fpnumber      while  s length    gt  n  amp  amp  s endsWith  0              s   s substring 0  s length  -1             return s

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Format price with grouping  rounding  and no unnecessary zeroes  in double   Rules   No zeroes at the end  2 0000   2  1 0100000   1 01  Two digits maximum after a point  2 010   2 01  0 20   0 2  Rounding after the 2nd digit after a point  1 994   1 99  1 995   2  1 006   1 01  0 0006 - gt  0  Returns 0  null -0   0  Adds       56 - 56  Grouping  101101 02    101 101 02   More examples   -99 985   - 99 99 10    10 10 00    10 20 01000089    20 01  It is written in Kotlin as a fun extension of Double  because it is used in Android   but it can be converted to Java easily  because Java classes were used         23 0 - gt   23       23 1 - gt   23 1       23 01 - gt   23 01       23 99 - gt   23 99       23 999 - gt   24       -0 0 - gt   0       -5 00 - gt  - 5       -5 019 - gt  - 5 02     fun Double  formatUserAsSum    String       return when           this    null    this    0 0 - gt   quot  0 quot          this   1    0 0 - gt  DecimalFormat  quot      0 -     0 quot   format this          else - gt  DecimalFormat  quot      0    -     0    quot   format this           How to use  var yourDouble  Double    -20 00 println yourDouble formatUserAsSum       will print - 20  yourDouble   null println yourDouble formatUserAsSum       will print  0  About DecimalFormat  https   docs oracle com javase 6 docs api java text DecimalFormat html

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This is what I came up with    private static String format final double dbl        return dbl   1    0   String valueOf dbl    String valueOf  int  dbl        It is a simple one-liner and only casts to int if it really needs to

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Here is an answer that actually works  combination of different answers here   public static String removeTrailingZeros double f        if f     int f            return String format   d    int f             return String format   f   f  replaceAll  0

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Use  if  d   1 0    0      return String format  quot  s quot   d   else     return String format  quot   0f quot   d    This should work with the extreme values supported by Double  It yields  0 12 12 12 144252 0

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I made a DoubleFormatter to efficiently convert a great numbers of double values to a nice presentable string  double horribleNumber   3598945 141658554548844  DoubleFormatter df   new DoubleFormatter 4  6      4   MaxInteger  6   MaxDecimal String beautyDisplay   df format horribleNumber     If the integer part of V has more than MaxInteger   gt  display V in scientific format  1 2345E 30   Otherwise  display in normal format  124 45678   the MaxDecimal decide numbers of decimal digits  trim with bankers  rounding   Here the code  import java math RoundingMode  import java text DecimalFormat  import java text DecimalFormatSymbols  import java text NumberFormat  import java util Locale   import com google common base Preconditions  import com google common base Strings          Convert a double to a beautiful String  US-local         double horribleNumber   3598945 141658554548844     DoubleFormatter df   new DoubleFormatter 4 6      String beautyDisplay   df format horribleNumber      String beautyLabel   df formatHtml horribleNumber         Manipulate 3 instances of NumberFormat to efficiently format a great number of double values      avoid to create an object NumberFormat each call of format           3 instances of NumberFormat will be reused to format a value v        if v  lt  EXP DOWN  uses nfBelow    if EXP DOWN  lt   v  lt   EXP UP  uses nfNormal    if EXP UP  lt  v  uses nfAbove       nfBelow  nfNormal and nfAbove will be generated base on the precision  parameter         author  DUONG Phu-Hiep     public class DoubleFormatter       private static final double EXP DOWN   1 e-3      private double EXP UP     always   10 maxInteger     private int maxInteger       private int maxFraction       private NumberFormat nfBelow       private NumberFormat nfNormal       private NumberFormat nfAbove        private enum NumberFormatKind  Below  Normal  Above       public DoubleFormatter int maxInteger  int maxFraction           setPrecision maxInteger  maxFraction              public void setPrecision int maxInteger  int maxFraction           Preconditions checkArgument maxFraction gt  0           Preconditions checkArgument maxInteger gt 0  amp  amp  maxInteger lt 17            if  maxFraction    maxFraction   amp  amp  maxInteger     maxInteger                return                     maxFraction    maxFraction          maxInteger    maxInteger          EXP UP    Math pow 10  maxInteger           nfBelow    createNumberFormat NumberFormatKind Below           nfNormal    createNumberFormat NumberFormatKind Normal           nfAbove    createNumberFormat NumberFormatKind Above              private NumberFormat createNumberFormat NumberFormatKind kind                If you do not use the Guava library  replace it with createSharp precision           final String sharpByPrecision   Strings repeat  quot   quot   maxFraction             NumberFormat f   NumberFormat getInstance Locale US               Apply bankers  rounding   this is the rounding mode that            statistically minimizes cumulative error when applied            repeatedly over a sequence of calculations         f setRoundingMode RoundingMode HALF EVEN            if  f instanceof DecimalFormat                DecimalFormat df    DecimalFormat  f              DecimalFormatSymbols dfs   df getDecimalFormatSymbols                    Set group separator to space instead of comma                dfs setGroupingSeparator                       Set Exponent symbol to minus  e  instead of  E              if  kind    NumberFormatKind Above                    dfs setExponentSeparator  quot e  quot      force to display the positive sign in the exponent part               else                   dfs setExponentSeparator  quot e quot                               df setDecimalFormatSymbols dfs                   Use exponent format if v is outside of  EXP DOWN EXP UP               if  kind    NumberFormatKind Normal                    if  maxFraction     0                        df applyPattern  quot     0 quot                      else                       df applyPattern  quot     0  quot  sharpByPrecision                                   else                   if  maxFraction     0                        df applyPattern  quot 0E0 quot                      else                       df applyPattern  quot 0  quot  sharpByPrecision  quot E0 quot                                                      return f             public String format double v            if  Double isNaN v                 return  quot - quot                     if  v  0                return  quot 0 quot                     final double absv   Math abs v            if  absv lt EXP DOWN                return nfBelow  format v                      if  absv gt EXP UP                return nfAbove  format v                      return nfNormal  format v                         Format and higlight the important part  integer part  amp  exponent part              public String formatHtml double v            if  Double isNaN v                 return  quot - quot                     return htmlize format v                          This is the base alogrithm  create a instance of NumberFormat for the value  then format it  It should        not be used to format a great numbers of value               We will never use this methode  it is here only to understanding the Algo principal                format v to string  precision  is numbers of digits after decimal         if EXP DOWN  lt   abs v   lt   EXP UP  display the normal format  124 45678        otherwise display scientist format with  1 2345e 30               pre-condition  precision  gt   1              Deprecated     public String formatInefficient double v                If you do not use Guava library  replace with createSharp precision           final String sharpByPrecision   Strings repeat  quot   quot   maxFraction             final double absv   Math abs v            NumberFormat f   NumberFormat getInstance Locale US               Apply bankers  rounding   this is the rounding mode that            statistically minimizes cumulative error when applied            repeatedly over a sequence of calculations         f setRoundingMode RoundingMode HALF EVEN            if  f instanceof DecimalFormat                DecimalFormat df    DecimalFormat  f              DecimalFormatSymbols dfs   df getDecimalFormatSymbols                    Set group separator to space instead of comma              dfs setGroupingSeparator                       Set Exponent symbol to minus  e  instead of  E               if  absv gt EXP UP                    dfs setExponentSeparator  quot e  quot      force to display the positive sign in the exponent part               else                   dfs setExponentSeparator  quot e quot                              df setDecimalFormatSymbols dfs                  use exponent format if v is out side of  EXP DOWN EXP UP               if  absv lt EXP DOWN    absv gt EXP UP                    df applyPattern  quot 0  quot  sharpByPrecision  quot E0 quot                  else                   df applyPattern  quot     0  quot  sharpByPrecision                                   return f format v                         Convert  quot 3 1416e 12 quot  to  quot  lt b gt 3 lt  b gt  1416e lt b gt  12 lt  b gt  quot         It is a html format of a number which highlight the integer and exponent part             private static String htmlize String s            StringBuilder resu   new StringBuilder  quot  lt b gt  quot            int p1   s indexOf                if  p1 gt 0                resu append s substring 0  p1                resu append  quot  lt  b gt  quot              else               p1   0                     int p2   s lastIndexOf  e            if  p2 gt 0                resu append s substring p1  p2                resu append  quot  lt b gt  quot                resu append s substring p2  s length                  resu append  quot  lt  b gt  quot              else               resu append s substring p1  s length                  if  p1  0                   resu append  quot  lt  b gt  quot                                    return resu toString             Note  I used two functions from the Guava library  If you don t use Guava  code it yourself         Equivalent to Strings repeat  quot   quot   n  of the Guava library      private static String createSharp int n        StringBuilder sb   new StringBuilder        for  int i 0  i lt n  i              sb append                 return sb toString

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new DecimalFormat         format 1 199      1 2    As pointed in the comments  this is not the right answer to the original question  That said  it is a very useful way to format numbers without unnecessary trailing zeros

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String s   String valueof  your int variable    while  g endsWith  0    amp  amp  g contains             g   g substring 0  g length   - 1       if  g endsWith                     g   g substring 0  g length   - 1

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In short  If you want to get rid of trailing zeros and locale problems  then you should use  double myValue   0 00000021d   DecimalFormat df   new DecimalFormat  quot 0 quot   DecimalFormatSymbols getInstance Locale ENGLISH    df setMaximumFractionDigits 340     340   DecimalFormat DOUBLE FRACTION DIGITS  System out println df format myValue      output  0 00000021  Explanation  Why other answers did not suit me   Double toString   or System out println or FloatingDecimal toJavaFormatString uses scientific notations if double is less than 10 -3 or greater than or equal to 10 7  double myValue   0 00000021d   String format  quot  s quot   myvalue     output  2 1E-7   by using  f  the default decimal precision is 6  otherwise you can hardcode it  but it results in extra zeros added if you have fewer decimals  Example   double myValue   0 00000021d   String format  quot   12f quot   myvalue      Output  0 000000210000   by using setMaximumFractionDigits 0   or   0f you remove any decimal precision  which is fine for integers longs but not for double  double myValue   0 00000021d   System out println String format  quot   0f quot   myvalue       Output  0  DecimalFormat df   new DecimalFormat  quot 0 quot     System out println df format myValue       Output  0   by using DecimalFormat  you are local dependent  In the French locale  the decimal separator is a comma  not a point   double myValue   0 00000021d   DecimalFormat df   new DecimalFormat  quot 0 quot     df setMaximumFractionDigits 340    System out println df format myvalue       Output  0 00000021  Using the ENGLISH locale makes sure you get a point for decimal separator  wherever your program will run    Why using 340 then for setMaximumFractionDigits  Two reasons   setMaximumFractionDigits accepts an integer  but its implementation has a maximum digits allowed of DecimalFormat DOUBLE FRACTION DIGITS which equals 340 Double MIN VALUE   4 9E-324 so with 340 digits you are sure not to round your double and lose precision

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String s    1 210000   while  s endsWith  0         s    s substring 0  s length   - 1        This will make the string to drop the tailing 0-s

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You said you choose to store your numbers with the double type  I think this could be the root of the problem  because it forces you to store integers into doubles  and therefore losing the initial information about the value s nature   What about storing your numbers in instances of the Number class  superclass of both Double and Integer  and rely on polymorphism to determine the correct format of each number  I know it may not be acceptable to refactor a whole part of your code due to that  but it could produce the desired output without extra code casting parsing  Example  import java util ArrayList  import java util List   public class UseMixedNumbers        public static void main String   args            List lt Number gt  listNumbers   new ArrayList lt Number gt              listNumbers add 232           listNumbers add 0 18           listNumbers add 1237875192           listNumbers add 4 58           listNumbers add 0           listNumbers add 1 2345            for  Number number   listNumbers                System out println number                       Will produce the following output  232 0 18 1237875192 4 58 0 1 2345

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If the idea is to print integers stored as doubles as if they are integers  and otherwise print the doubles with the minimum necessary precision   public static String fmt double d        if d     long  d          return String format   d   long d       else         return String format   s  d       Produces   232 0 18 1237875192 4 58 0 1 2345   And does not rely on string manipulation

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Use a DecimalFormat and setMinimumFractionDigits 0

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new DecimalFormat  00     format 20 236    out  20 2  new DecimalFormat  00     format 2 236    out  02 2    0 for minimum number of digits Renders   digits

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if  d    Math floor d         return String format    0f   d     else       return Double toString d

[java] How to nicely format floating numbers to string without unnecessary decimal 0's

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