JDBC Lock a row using SELECT FOR UPDATE, doesn't work

I am having issues with MySQL's SELECT .. FOR UPDATE, here is the query I am trying to run:

SELECT * FROM tableName WHERE HostName='UnknownHost' 
        ORDER BY UpdateTimestamp asc limit 1 FOR UPDATE

After this, the concerned thread will do an UPDATE and change the HostName, which is then it should unlock the row.

I am running a multi-threaded java application, so 3 threads are running this SQL statement, but when thread 1 runs this, it doesn't lock its results from thread 2 & 3. Therefore threads 2 & 3 are getting the same results and they could update the same row.

Also each thread is on its own mysql connection.

I'm using Innodb, with transaction-isolation = READ-COMMITTED, and the Autocommit is off before executing the select for update

may I miss something? OR perhaps there is a better solution? Thanks a lot.

Code :

public BasicJDBCDemo()
{
    Le_Thread newThread1=new Le_Thread();
    Le_Thread newThread2=new Le_Thread();
    newThread1.start();
    newThread2.start();         
}

Thread :

class Le_Thread extends Thread  
{

    public void run() 
    {
    tring name = Thread.currentThread().getName();
        System.out.println( name+": Debut.");
    long oid=Util.doSelectLockTest(name);
    Util.doUpdateTest(oid,name);        
    }

}

Select :

public  static long doSelectLockTest(String threadName)
  {
    System.out.println("[OUTPUT FROM SELECT Lock ]...threadName="+threadName);
    PreparedStatement pst = null;
    ResultSet rs=null;
    Connection conn=null;
    long oid=0;
    try
    {
     String query = "SELECT * FROM table WHERE Host=? 
                               ORDER BY Timestamp asc limit 1 FOR UPDATE";


      conn=getNewConnection();
      pst = conn.prepareStatement(query);
      pst.setString(1, DbProperties.UnknownHost);
      System.out.println("pst="+threadName+"__"+p