Add leading zeroes to number in Java

Question

Is there a better way of getting this result  This function fails if num has more digits than digits  and I feel like it should be in the library somewhere  like Integer toString x   3d   or something   static String intToString int num  int digits        StringBuffer s   new StringBuffer digits       int zeroes   digits -  int   Math log num    Math log 10   - 1       for  int i   0  i  lt  zeroes  i              s append 0             return s append num  toString

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Another option is to use DecimalFormat to format your numeric String  Here is one other way to do the job without having to use String format if you are stuck in the pre 1 5 world   static String intToString int num  int digits        assert digits  gt  0    Invalid number of digits           create variable length array of zeros     char   zeros   new char digits       Arrays fill zeros   0           format number as String     DecimalFormat df   new DecimalFormat String valueOf zeros         return df format num

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Since Java 1 5 you can use the String format method  For example  to do the same thing as your example  String format   String format  quot  0 d quot   digits   String result   String format format  num   return result   In this case  you re creating the format string using the width specified in digits  then applying it directly to the number  The format for this example is converted as follows     -- gt    0  -- gt  0  d -- gt   lt value of digits gt  d  -- gt  d  So if digits is equal to 5  the format string becomes  05d which specifies an integer with a width of 5 printing leading zeroes  See the java docs for String format for more information on the conversion specifiers

User · Answer

Another option is to use DecimalFormat to format your numeric String  Here is one other way to do the job without having to use String format if you are stuck in the pre 1 5 world   static String intToString int num  int digits        assert digits  gt  0    Invalid number of digits           create variable length array of zeros     char   zeros   new char digits       Arrays fill zeros   0           format number as String     DecimalFormat df   new DecimalFormat String valueOf zeros         return df format num

User · Answer

Since Java 1 5 you can use the String format method  For example  to do the same thing as your example  String format   String format  quot  0 d quot   digits   String result   String format format  num   return result   In this case  you re creating the format string using the width specified in digits  then applying it directly to the number  The format for this example is converted as follows     -- gt    0  -- gt  0  d -- gt   lt value of digits gt  d  -- gt  d  So if digits is equal to 5  the format string becomes  05d which specifies an integer with a width of 5 printing leading zeroes  See the java docs for String format for more information on the conversion specifiers

User · Answer

How about just   public static String intToString int num  int digits        String output   Integer toString num       while  output length    lt  digits  output    0    output      return output

User · Answer

Another option is to use DecimalFormat to format your numeric String  Here is one other way to do the job without having to use String format if you are stuck in the pre 1 5 world   static String intToString int num  int digits        assert digits  gt  0    Invalid number of digits           create variable length array of zeros     char   zeros   new char digits       Arrays fill zeros   0           format number as String     DecimalFormat df   new DecimalFormat String valueOf zeros         return df format num

User · Answer

Since Java 1 5 you can use the String format method  For example  to do the same thing as your example  String format   String format  quot  0 d quot   digits   String result   String format format  num   return result   In this case  you re creating the format string using the width specified in digits  then applying it directly to the number  The format for this example is converted as follows     -- gt    0  -- gt  0  d -- gt   lt value of digits gt  d  -- gt  d  So if digits is equal to 5  the format string becomes  05d which specifies an integer with a width of 5 printing leading zeroes  See the java docs for String format for more information on the conversion specifiers

User · Answer

String format  https   docs oracle com javase 1 5 0 docs api java util Formatter html syntax   In your case it will be    String formatted   String format   03d   num      0 - to pad with zeros 3 - to set width to 3

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In case of your jdk version less than 1 5  following option can be used       int iTest   2      StringBuffer sTest   new StringBuffer  000000      if the string size is 6     sTest append String valueOf iTest        System out println sTest substring sTest length  -6  sTest length

User · Answer

String format  https   docs oracle com javase 1 5 0 docs api java util Formatter html syntax   In your case it will be    String formatted   String format   03d   num      0 - to pad with zeros 3 - to set width to 3

User · Answer

String format  https   docs oracle com javase 1 5 0 docs api java util Formatter html syntax   In your case it will be    String formatted   String format   03d   num      0 - to pad with zeros 3 - to set width to 3

User · Answer

Another option is to use DecimalFormat to format your numeric String  Here is one other way to do the job without having to use String format if you are stuck in the pre 1 5 world   static String intToString int num  int digits        assert digits  gt  0    Invalid number of digits           create variable length array of zeros     char   zeros   new char digits       Arrays fill zeros   0           format number as String     DecimalFormat df   new DecimalFormat String valueOf zeros         return df format num

User · Answer

How about just   public static String intToString int num  int digits        String output   Integer toString num       while  output length    lt  digits  output    0    output      return output

User · Answer

In case of your jdk version less than 1 5  following option can be used       int iTest   2      StringBuffer sTest   new StringBuffer  000000      if the string size is 6     sTest append String valueOf iTest        System out println sTest substring sTest length  -6  sTest length

User · Answer

Since Java 1 5 you can use the String format method  For example  to do the same thing as your example  String format   String format  quot  0 d quot   digits   String result   String format format  num   return result   In this case  you re creating the format string using the width specified in digits  then applying it directly to the number  The format for this example is converted as follows     -- gt    0  -- gt  0  d -- gt   lt value of digits gt  d  -- gt  d  So if digits is equal to 5  the format string becomes  05d which specifies an integer with a width of 5 printing leading zeroes  See the java docs for String format for more information on the conversion specifiers

User · Answer

String format  https   docs oracle com javase 1 5 0 docs api java util Formatter html syntax   In your case it will be    String formatted   String format   03d   num      0 - to pad with zeros 3 - to set width to 3

[java] Add leading zeroes to number in Java?

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