Split string of numbers into individual numbers

Question

How could I split the numbers in the string "542" into individual digits? On my desktop I can split the numbers using String.split("") and it works fine. But when run on Android, I get a NumberFormatException: Invalid int: "". This is my code:

public void render(int n, SpriteBatch batch) {
    String[] numbers = String.valueOf(n).split("");
    for(int i = 0; i < numbers.length; i++) 
        batch.draw(Assets.numbers[0][Integer.valueOf(numbers[i])], pos.x + (50 * i), pos.y);
}

Is there an alternative way?

You can just iterate over each digit as characters. Careful with negative values. — Sotirios Delimanolis, Jun 22 '14 at 18:26
It is very unlikely that a NFE should be thrown on the context of `String.split(String regex)` - there just isn't a number to convert. — laune, Jun 22 '14 at 18:35

score 3 · Accepted Answer · answered Jun 22 '14 at 18:29

3

You can use String.charAt, that will give you a Character. Removing '0' will give you a value from 0 to 9.

public void render(int n, SpriteBatch batch) {
    String string = Integer.toString(n);
    for(int i = 0; i < string.length(); ++i) 
        batch.draw(Assets.numbers[0][string.charAt(i) - '0'],
                   pos.x + (50 * i), pos.y);
}

answered Jun 22 '14 at 18:29

Nicolas Defranoux

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Note that Integer.toString(n) and String.valueOf(n) should have the exact same effect. – Nicolas Defranoux Jun 22 '14 at 18:32

score 2 · Answer 2 · answered Jun 22 '14 at 18:44

2

Your use of String.split("") will always leave the first index empty (that is, the String: ""). This is why you are getting NumberFormatException: Invalid int: "" when trying to run Integer.valueOf(numbers[0]).

Suggest using string.charAt(index) to iterate over the characters in String.valueOf(n) instead.

answered Jun 22 '14 at 18:44

Halvor Holsten Strand

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"String.split("") will always leave the first index empty", not always, [at least not from Java 8](http://stackoverflow.com/questions/22718744/why-does-split-in-java-8-sometimes-removes-empty-strings-if-they-are-at-start-of). – Pshemo Jun 22 '14 at 23:04

score 1 · Answer 3 · answered Jun 22 '14 at 23:21

Splitting on "" will cause the first element of the resulting array to be a blank, because the blank regex matches everywhere, including start of input.

You need to split after every character:

String[] digits = str.split("(?<=.)");

This regex is a look behind that assets there is a character before the match. Look behinds are non-consuming, so you don't lose any input making the split.

Split string of numbers into individual numbers

3 Answers3