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<=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<=newGuess.length; i++) {         System.out.println(newGuess[i]);     } } 

But an exception is thrown:

Exception in thread "main" java.lang.NumberFormatException: For input string: ""
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?

Answer 1

The immediate problem is due to you using <= temp.length() instead of < 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 < temp.length(); i++) {     newGuess[i] = temp.charAt(i) - '0'; } 

You need to make the same change to use < 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 < in the condition, rather than <=.