LDAP: How to authenticate user with connection details

I am not able to authenticate a user using LDAP. I have got following details:

URL=ldap://10.10.10.10:389 
LDAP BASE:DC=lab2,DC=ins 
LDAP Bind Account: CN=Ldap Bind,OU=Service Accounts,OU=TECH,DC=lab2,DC=ins 
LDAP Bind Account Pw: secret 

I can search a sAMAccountName value using above details, but how to authenticate a user with user name and password?
If you follow my previous questions then you will understand that, I am successfully able to connect to LDAP server but not able to authenticate him.
User to authenticate:

user: someusername
password: somepwd

I am not able to connect to LDAP server with 'somepwd' and how should I use someusername. I am able to search given user as sAMAccountName.

This is a mashup of stuff I found in various places. It should put you along the correct path if you don't want to use the UnboundID SDK. This isn't production quality, you might want to add the SSL stuff in here if your shop supports it.

public static Boolean validateLogin(String userName, String userPassword) {
    Hashtable<String, String> env = new Hashtable<String, String>();


    env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.ldap.LdapCtxFactory");
    env.put(Context.PROVIDER_URL, "ldap://" + LDAP_SERVER + ":" + LDAP_SERVER_PORT + "/" + LDAP_BASE_DN);

    // To get rid of the PartialResultException when using Active Directory
    env.put(Context.REFERRAL, "follow");

    // Needed for the Bind (User Authorized to Query the LDAP server) 
    env.put(Context.SECURITY_AUTHENTICATION, "simple");
    env.put(Context.SECURITY_PRINCIPAL, LDAP_BIND_DN);
    env.put(Context.SECURITY_CREDENTIALS, LDAP_BIND_PASSWORD);

    DirContext ctx;
    try {
       ctx = new InitialDirContext(env);
    } catch (NamingException e) {
       throw new RuntimeException(e);
    }

    NamingEnumeration<SearchResult> results = null;

    try {
       SearchControls controls = new SearchControls();
       controls.setSearchScope(SearchControls.SUBTREE_SCOPE); // Search Entire Subtree
       controls.setCountLimit(1);   //Sets the maximum number of entries to be returned as a result of the search
       controls.setTimeLimit(5000); // Sets the time limit of these SearchControls in milliseconds

       String searchString = "(&(objectCategory=user)(sAMAccountName=" + userName + "))";

       results = ctx.search("", searchString, controls);

       if (results.hasMore()) {

           SearchResult result = (SearchResult) results.next();
           Attributes attrs = result.getAttributes();
           Attribute dnAttr = attrs.get("distinguishedName");
           String dn = (String) dnAttr.get();

           // User Exists, Validate the Password

           env.put(Context.SECURITY_PRINCIPAL, dn);
           env.put(Context.SECURITY_CREDENTIALS, userPassword);

           new InitialDirContext(env); // Exception will be thrown on Invalid case
           return true;
       } 
       else 
           return false;

    } catch (AuthenticationException e) { // Invalid Login

        return false;
    } catch (NameNotFoundException e) { // The base context was not found.

        return false;
    } catch (SizeLimitExceededException e) {
        throw new RuntimeException("LDAP Query Limit Exceeded, adjust the query to bring back less records", e);
    } catch (NamingException e) {
       throw new RuntimeException(e);
    } finally {

       if (results != null) {
          try { results.close(); } catch (Exception e) { /* Do Nothing */ }
       }

       if (ctx != null) {
          try { ctx.close(); } catch (Exception e) { /* Do Nothing */ }
       }
    }
}