Generate unique 10 char string

Question

Hi,
i have to generate a unique 10 char string ( a string with length of 10 ) which has numbers and alphabets with no special characters, is there any code of doing it
Ashish

Answer 1

class UniqueString {
  private static final int NUM_CHARS = 10;
  private static int[] lastString = new int[NUM_CHARS];
  private static final String chars =
"0123456789abcdefghijklmonpqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"; 
  static String getUnique() {   
     char[] buf = new char[NUM_CHARS];   
     carry(lastString, buf.length-1);
     for(int i=0;i<buf.length;i++) {
       buf[i] = chars.charAt(lastString);
return new String(buf);
private static void carry(int[] ca, int index) {
if(ca[index]==(chars.length()-1)) {
ca[index]=0;
carry(ca,--index);
else ca[index]= ca[index]+1;
public static void main(String[] args) {
for(int i=0;i<10000;i++)
     System.out.println(UniqueString.getUnique());
Guarenteed to be unique within one VM instance.
matfud