How to extract numbers from a string and get an array of ints

Question

I have a String variable  basically an English sentence with an unspecified number of numbers  and I d like to extract all the numbers into an array of integers  I was wondering whether there was a quick solution with regular expressions     I used Sean s solution and changed it slightly   LinkedList lt String gt  numbers   new LinkedList lt String gt      Pattern p   Pattern compile    d     Matcher m   p matcher line    while  m find         numbers add m group

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Pattern p   Pattern compile   0-9      Matcher m   p matcher myString   while  m find          int n   Integer parseInt m group            append n to list      convert list to array  etc   You can actually replace  0-9  with  d  but that involves double backslash escaping  which makes it harder to read

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for rational numbers use this one     0-9    0-9      0-9    0-9      0-9

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Using Java 8  you can do   String str    There 0 are 1 some -2-34 -numbers 567 here 890     int   ints   Arrays stream str replaceAll  -     -   split    -  d                        filter s - gt   s matches  -                       mapToInt Integer  parseInt  toArray    System out println Arrays toString ints       prints  0  1  -2  -34  567  890    If you don t have negative numbers  you can get rid of the replaceAll  and use  s isEmpty   in filter   as that s only to properly split something like 2-34  this can also be handled purely with regex in split  but it s fairly complicated    Arrays stream turns our String   into a Stream lt String gt    filter gets rid of the leading and trailing empty strings as well as any - that isn t part of a number   mapToInt Integer  parseInt  toArray   calls parseInt on each String to give us an int       Alternatively  Java 9 has a Matcher results method  which should allow for something like   Pattern p   Pattern compile  -   d     Matcher m   p matcher  There 0 are 1 some -2-34 -numbers 567 here 890      int   ints   m results   map MatchResults  group  mapToInt Integer  parseInt  toArray    System out println Arrays toString ints       prints  0  1  -2  -34  567  890      As it stands  neither of these is a big improvement over just looping over the results with Pattern   Matcher as shown in the other answers  but it should be simpler if you want to follow this up with more complex operations which are significantly simplified with the use of streams

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StringBuffer sBuffer   new StringBuffer      Pattern p   Pattern compile   0-9    0-9    0-9    0-9    0-9        Matcher m   p matcher str     while  m find          sBuffer append m group           return sBuffer toString      This is for extracting numbers retaining the decimal

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I found this expression simplest  String   extractednums   msg split      D

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Extract all real numbers using this   public static ArrayList lt Double gt  extractNumbersInOrder String str        str   a       double   returnArray   new double           ArrayList lt Double gt  list   new ArrayList lt Double gt         String singleNum         Boolean numStarted      for char c str toCharArray              if isNumber c                singleNum  c             else               if  singleNum equals          number ended                 list add Double valueOf singleNum                    System out println singleNum                   singleNum                                        return list      public static boolean isNumber char c       if Character isDigit c   c   -   c       c                return true        else           return false

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The accepted answer detects digits but does not detect formated numbers  e g  2 000  nor decimals  e g  4 8  For such use -   d     d          d    Pattern p   Pattern compile  quot -   d     d          d   quot    List lt String gt  numbers   new ArrayList lt String gt     Matcher m   p matcher  quot Government has distributed 4 8 million textbooks to 2 000 schools quot    while  m find            numbers add m group          System out println numbers    Output   4 8  2 000

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What about to use replaceAll java lang String method        String str    qwerty-1qwerty-2 455 f0gfg 4             str   str replaceAll    - 0-9                System out println Arrays asList str trim   split           Output    -1  -2  455  0  4      Description    - 0-9        and   delimites a set of characters to be single matched  i e   only one time in any order   Special identifier used in the beginning of the set  used to indicate to match all characters not present in the delimited set  instead of all characters present in the set    Between one and unlimited times  as many times as possible  giving back as needed -  One of the characters    -    and         0-9 A character in the range between    0    and    9

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If you want to exclude numbers that are contained within words  such as bar1 or aa1bb  then add word boundaries  b to any of the regex based answers  For example   Pattern p   Pattern compile    b-   d   b    Matcher m   p matcher  9There 9are more9 th9an -2 and less than 12 numbers here9    while  m find        System out println m group         displays   2 12

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Fraction and grouping characters for representing real numbers may differ between languages  The same real number could be written in very different ways depending on the language   The number two million in German  2 000 000 00  and in English  2 000 000 00  A method to fully extract real numbers from a given string in a language agnostic way   public List lt BigDecimal gt  extractDecimals final String s  final char fraction  final char grouping        List lt BigDecimal gt  decimals   new ArrayList lt BigDecimal gt           Remove grouping character for easier regexp extraction     StringBuilder noGrouping   new StringBuilder        int i   0      while i  gt   0  amp  amp  i  lt  s length              char c   s charAt i           if c    grouping                int prev   i-1  next   i 1              boolean isValidGroupingChar                       prev  gt   0  amp  amp  Character isDigit s charAt prev    amp  amp                      next  lt  s length    amp  amp  Character isDigit s charAt next                                 if  isValidGroupingChar                  noGrouping append c               i              else               noGrouping append c               i                          the     character has to be escaped in regular expressions     String fractionRegex   fraction    POINT           String valueOf fraction       Pattern p   Pattern compile  -    d     fractionRegex      d    d          Matcher m   p matcher noGrouping       while  m find              String match   m group   replace COMMA  POINT           decimals add new BigDecimal match              return decimals

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Pattern p   Pattern compile  -   d     Matcher m   p matcher  There are more than -2 and less than 12 numbers here    while  m find        System out println m group             prints -2 and 12     -  matches a leading negative sign -- optionally   d matches a digit  and we need to write   as    in a Java String though  So   d  matches 1 or more digits

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public static String extractNumberFromString String number        String num   number replaceAll    0-9               return num replaceAll               extracts only numbers from string

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I would suggest to check the ASCII values to extract numbers from a String  Suppose you have an input String as myname12345 and if you want to just extract the numbers 12345 you can do so by first converting the String to Character Array then use the following pseudocode       for int i 0  i  lt  CharacterArray length  i                  if  a i   gt  48  amp  amp  a i   lt   58              System out print a i            once the numbers are extracted append them to an array  Hope this helps

[java] How to extract numbers from a string and get an array of ints?

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