quickos

public class qsort{
public static void quicksort(char[] a, int i, int j)
{
    if(j-i < 2) return;
    int m = i+(j-i)/2;
    char b = a[m];
    a[m] = a[i];
    a[i] = b;
    int r = i+1;
    for(int s = r; s!=j; s=s+1)
    {
        if(a[s] < b)
        {
            char tmp = a[s];
            a[s] = a[r];
            a[r] = tmp;
            r = r+1;
        }
    }
    r=r-1;
    a[i]=a[r];
    a[r]=b;
    quicksort(a,i,r);
    quicksort(a,r+1,j);
}
public Character[] toCharArray( String s )
{
   int len = s.length();
   Character[] array = new Character[len];
   for (int i = 0; i < len ; i++) {
      array[i] = new Character(s.charAt(i));
   }
   return array;
}
    public static void main(String[] args)
    {
        String input = StdIn.readString();
        char[] stc = input.toCharArray();
        quicksort(stc,0,stc.length);
        for(int i = 0; i<stc.length; i++)
        {
            System.out.print(stc[i]);
        }
    }
}