java password generator

gistfile1.txt

*way 1. 

import java.security.SecureRandom;

public final class SessionIdentifierGenerator {
  private SecureRandom random = new SecureRandom();

  public String nextSessionId() {
    return new BigInteger(130, random).toString(32);
  }
}

*way 2.

static final String AB = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
static Random rnd = new Random();

String randomString( int len ) 
{
   StringBuilder sb = new StringBuilder( len );
   for( int i = 0; i < len; i++ ) 
      sb.append( AB.charAt( rnd.nextInt(AB.length()) ) );
   return sb.toString();
}

*way 3.

public static String RandomAlphaNumericString(int size){
    String chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    String ret = "";
    int length = chars.length();
    for (int i = 0; i < size; i ++){
        ret += chars.split("")[ (int) (Math.random() * (length - 1)) ];
    }
    return ret;
}

*way 4.

// "0123456789" + "ABCDE...Z"
String validCharacters = $('0', '9').join() + $('A', 'Z').join();

String randomString(int length) {
    return $(validCharacters).shuffle().slice(length).toString();
}

@Test

public void buildFiveRandomStrings() {
    for (int i : $(5)) {
        System.out.println(randomString(12));
    }
}

*way 5.

public static String getRandomString(int length) 
{
   String randomStr = UUID.randomUUID().toString();
   while(randomStr.length() < length) {
       randomStr += UUID.randomUUID().toString();
   }
   return randomStr.substring(0, length);
}