RandomString.java

import java.util.Random;

//http://stackoverflow.com/questions/41107/how-to-generate-a-random-alpha-numeric-string
public class RandomString {

 private static final char[] symbols;

 static {
 StringBuilder tmp = new StringBuilder();
 for (char ch = '0'; ch <= '9'; ++ch)
 tmp.append(ch);
 for (char ch = 'a'; ch <= 'z'; ++ch)
 tmp.append(ch);
 symbols = tmp.toString().toCharArray();
 }

 private final Random random = new Random();

 private final char[] buf;

 public RandomString(int length) {
 if (length < 1)
 throw new IllegalArgumentException("length < 1: " + length);
 buf = new char[length];
 }

 public String nextString() {
 for (int idx = 0; idx < buf.length; ++idx)
 buf[idx] = symbols[random.nextInt(symbols.length)];
 return new String(buf);
 }
}