Convert an integer to an array of digits

Question

I try to convert an integer to an array  For example  1234 to int   arr    1 2 3 4    I ve written a function  public static void convertInt2Array int guess         String temp   Integer toString guess       String temp2      int temp3      int    newGuess   new int temp length         for int i 0  i lt  temp length    i              if  i  temp length                  temp2   temp substring i  i 1             else               temp2   temp substring i                 System out println i                     temp3    Integer parseInt temp2           newGuess i    temp3             for int i 0  i lt  newGuess length  i              System out println newGuess i             But an exception is thrown   Exception in thread  quot main quot  java lang NumberFormatException  For input string   quot  quot   at java lang NumberFormatException forInputString NumberFormatException java 65    at java lang Integer parseInt Integer java 504   at java lang Integer parseInt Integer java 527   at q4 test convertInt2Array test java 28   at q4 test main test java 14   Java Result  1   How can I fix this

User · Answer

Let s solve that using recursion    ArrayList lt Integer gt  al   new ArrayList lt  gt      void intToArray int num       if  num    0           int temp   num  10          num    10          intToArray num           al add temp            Explanation  Suppose the value of num is 12345  During the first call of the function  temp holds the value 5 and a value of num   1234  It is again passed to the function  and now temp holds the value 4 and the value of num is 123    This function calls itself till the value of num is not equal to 0  Stack trace   temp - 5   num - 1234  temp - 4   num - 123  temp - 3   num - 12  temp - 2   num - 1  temp - 1   num - 0  And then it calls the add method of ArrayList and the value of temp is added to it  so the value of list is   ArrayList - 1  ArrayList - 1 2  ArrayList - 1 2 3  ArrayList - 1 2 3 4  ArrayList - 1 2 3 4 5

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You can do something like this  public int   convertDigitsToArray int n         int    temp   new int String valueOf n  length        Calculate the length of digits     int i   String valueOf n  length  -1       Initialize the value to the last index      do           temp i    n   10          n   n   10          i--        while n gt 0        return temp     This will also maintain the order

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You can just do  char   digits   string toCharArray    And then you can evaluate the chars as integers  For example  char   digits    quot 12345 quot  toCharArray    int digit   Character getNumericValue digits 0    System out println digit      Prints 1

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Here is the function that takes an integer and return an array of digits  static int   Int to array int n        int j   0      int len   Integer toString n  length        int   arr   new int len       while n  0                arr len-j-1    n   10          n   n   10          j              return arr

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I can not add comments to the decision of Vladimir  but you can immediately make an array deployed in the right direction  Here is my solution  public static int   splitAnIntegerIntoAnArrayOfNumbers  int a        int temp   a      ArrayList lt Integer gt  array   new ArrayList lt Integer gt         do          array add temp   10           temp    10        while   temp  gt  0        int   arrayOfNumbers   new int array size         for int i   0  j   array size  -1  i  lt  array size    i   j--           arrayOfNumbers  j    array get i       return arrayOfNumbers     Important  This solution will not work for negative integers

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I can t add comments to Vladimir s solution  but I think that this is more efficient also when your initial numbers could be also below 10  This is my proposal  int temp   test  ArrayList lt Integer gt  array   new ArrayList lt Integer gt     do    array add temp   10     temp    10    while   temp  gt  1    Remember to reverse the array

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In Scala  you can do it like  def convert a  Int  acc  List Int    Nil   List Int      if  a  gt  0  convert a   10  a   10    acc  else acc  In one line and without reversing the order

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The immediate problem is due to you using  lt   temp length   instead of  lt  temp length    However  you can achieve this a lot more simply  Even if you use the string approach  you can use   String temp   Integer toString guess   int   newGuess   new int temp length     for  int i   0  i  lt  temp length    i          newGuess i    temp charAt i  -  0       You need to make the same change to use  lt  newGuess length   when printing out the content too - otherwise for an array of length 4  which has valid indexes 0  1  2  3  you ll try to use newGuess 4   The vast majority of for loops I write use  lt  in the condition  rather than  lt

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It would be much simpler to use the String split method  public static void fn int guess        String   sNums   Integer toString guess  split  quot  quot        for  String s   nums

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The  lt   in the for statement should be a  lt   BTW  it is possible to do this much more efficiently without using strings  but instead using  10 and  10 of integers

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You don t need to convert int to String  Just use   10 to get the last digit and then divide your int by 10 to get to the next one  int temp   test  ArrayList lt Integer gt  array   new ArrayList lt Integer gt     do      array add temp   10       temp    10    while   temp  gt  0    This will leave you with ArrayList containing your digits in reverse order  You can easily revert it if it s required and convert it to int

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Try this    int num   1234    String s   Integer toString num     int   intArray   new int s length        for int i 0  i lt s length    i         intArray i    Character getNumericValue s charAt i

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Use  public static void main String   args        int num   1234567      int   digits   Integer toString num  chars   map c - gt  c- 0   toArray        for int d   digits          System out print d      The main idea is  Convert the int to its String value Integer toString num     Get a stream of int that represents the ASCII value of each char  digit  composing the String version of our integer Integer toString num  chars      Convert the ASCII value of each character to its value  To get the actual int value of a character  we have to subtract the ASCII code value of the character  0  from the ASCII code of the actual character  To get all the digits of our number  this operation has to be applied on each character  corresponding to the digit  composing the string equivalent of our number which is done by applying the map function below to our IntStream  Integer toString num  chars   map c - gt  c- 0      Convert the stream of int to an array of int using toArray     Integer toString num  chars   map c - gt  c- 0   toArray

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Call this function    public int   convertToArray int number        int i   0      int length    int  Math log10 number       int divisor    int  Math pow 10  length       int temp     new int length   1        while  number    0            temp i    number   divisor          if  i  lt  length                  i                    number   number   divisor          if  i    0                divisor   divisor   10                      return temp

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2021 Answer      This single line will do the trick  Array from String 12345   Number    Example  x000D   x000D  const numToSeparate   12345   const arrayOfDigits   Array from String numToSeparate   Number    console log arrayOfDigits        1 2 3 4 5  x000D   x000D   x000D   Explanation 1- String numToSeparate  will convert the number 12345 into a string  returning  12345  2- The Array from   method creates a new Array instance from an array-like or iterable object  the string  12345  is an iterable object  so it will create an Array from it  3- But  in the process of automatically creating this new array  the Array from   method will first pass any iterable element  every character in this case eg   1    2    to the function we set to him as a second parameter  which is the Number function in this case 4- The Number function will take any string character and will convert it into a number eg  Number  1    will return 1  5- These numbers will be added one by one to a new array and finally this array of numbers will be returned  Summary The code line Array from String numToSeparate   Number   will convert the number into a string  take each character of that string  convert it into a number and put in a new array  Finally  this new array of numbers will be returned

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public static void main String k            System out println   NUMBER OF VALUES    k length       int arrymy   new int k length       for  int i   0  i  lt  k length  i                  int newGues   Integer parseInt k i            arrymy i    newGues

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You don t have to use substring        Use temp charAt i  to get a digit and use the following code to convert char to int   char c    7   int i   c -  0   System out println i

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First take input from the user as int  convert it into String  and make a character array of size of str length    Now populate a character array with a for loop using charAt    Scanner sc   new Scanner System in   int num   sc nextInt    String str   Integer toString num   char    ch   new char  str length      for int i 0  i lt str length    i          ch i    str charAt i      for char c  ch        System out print c   quot   quot

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temp2   temp substring i   will always return the empty string      Instead  your loop should have the condition i lt temp length    And temp2 should always be temp substring i  i 1     Similarly when you re printing out newGuess  you should loop up to newGuess length but not including  So your condition should be i lt newGuess length

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I can suggest the following method   Convert the number to a string   convert the string into an array of characters   convert the array of characters into an array of integers  Here comes my code  public class test        public static void main String   args             int num1   123456     Example 1         int num2   89786775     Example 2          String str1   Integer toString num1      Converts num1 into String         String str2   Integer toString num2      Converts num2 into String          char   ch1   str1 toCharArray       Gets str1 into an array of char         char   ch2   str2 toCharArray       Gets str2 into an array of char          int   t1   new int ch1 length      Defines t1 for bringing ch1 into it         int   t2   new int ch2 length      Defines t2 for bringing ch2 into it          for int i 0 i lt ch1 length i       Watch the ASCII table             t1 i    int  ch1 i -48     ch1 i  is 48 units more than what we want          for int i 0 i lt ch2 length i       Watch the ASCII table             t2 i    int  ch2 i -48     ch2 i  is 48 units more than what we want

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You can use  private int   createArrayFromNumber int number        String str    new Integer number   toString        char   chArr   str toCharArray        int   arr   new int chArr length       for  int i   0  i lt  chArr length  i              arr i    Character getNumericValue chArr i              return arr

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Use  int count   0  String newString   n    quot  quot   char    stringArray   newString toCharArray    int    intArray   new int stringArray length   for  char i   stringArray      int m   Character getNumericValue i     intArray count    m    count    1    return intArray   You ll have to put this into a method

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I modified Jon Skeet s accepted answer as it does not accept negative values  This now accepts and converts the number appropriately  public static void main String   args        int number   -1203      boolean isNegative   false      String temp   Integer toString number        if temp charAt 0     -             isNegative   true            int len   temp length        if isNegative            len   len - 1            int   myArr   new int len        for  int i   0  i  lt  len  i              if  isNegative                myArr i    temp charAt i   1  -  0                     if  isNegative                myArr i    temp charAt i  -  0                        if  isNegative            for  int i   0  i  lt  len  i                  myArr i    myArr i     -1                        for  int k   myArr            System out println k            Output -1 -2 0 -3

[java] Convert an integer to an array of digits

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