int to char[] conversion without String-class?

[Till Stoschus]

Hi,

following code converts an int to a char[] as its string represenation:

  
int i = 1982;
String s = String.valueOf(i);
char[] c = s.toCharArray();
// c is {'1','9','8','2'}  

Is there an easy way to do this without the "temporary" string so that no further object is created on the heap (only c should be on the heap)?

Thanks!
Tillux

[Rob Spoor]

You can use / 10 and % 10. The biggest issue with this is getting an array that's big enough. java.lang.Integer uses the following code for that:

    final static int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999,
                                      99999999, 999999999, Integer.MAX_VALUE };

    // Requires positive x
    static int stringSize(int x) {
        for (int i=0; ; i++)
            if (x <= sizeTable[i])
                return i+1;
    }

This code is called as follows:

    public static String toString(int i) {
        if (i == Integer.MIN_VALUE)
            return "-2147483648";
        int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i);
        char[] buf = new char[size];
        getChars(i, size, buf);
        return new String(0, size, buf);
    }

Using this you should be able to work out the rest.

[Till Stoschus]

Hi Rob,
i played a little with the sourcecode of Integer class. this solved my problem. Thanks!!!
Tillux

[Rob Spoor]

You're welcome.