Create a random string

import java.util.Random;

/**

* @author E. Kaparulin

*/

public class RandomString {

        private final char[] alphanumeric=alphanumeric();

            private final Random rand;

            public RandomString(){this(null);}

            public RandomString(Random rand){

              this.rand=(rand!=null) ? rand : new Random();

            }

            public String get(int len){

                StringBuffer out=new StringBuffer();

                while(out.length() < len){

                    int idx=Math.abs(( rand.nextInt() % alphanumeric.length ));

                    out.append(alphanumeric[idx]);

                }

                return out.toString();

            }

            // create alphanumeric char array

            private char[] alphanumeric(){

                StringBuffer buf=new StringBuffer(128);

                for(int i=48; i<= 57;i++)buf.append((char)i); // 0-9

                for(int i=65; i<= 90;i++)buf.append((char)i); // A-Z

                for(int i=97; i<=122;i++)buf.append((char)i); // a-z

                return buf.toString().toCharArray();

            }

}