So after getting the LdapContext, we could now retrieve a specific user account information using the SearchControls class

RetrieveUserAttributes.java

import java.util.Hashtable;
import javax.naming.Context;
import javax.naming.NamingEnumeration;
import javax.naming.NamingException;
import javax.naming.directory.Attributes;
import javax.naming.directory.SearchControls;
import javax.naming.directory.SearchResult;
import javax.naming.ldap.InitialLdapContext;
import javax.naming.ldap.LdapContext;

public class RetrieveUserAttributes {

	public static void main(String[] args) {
		RetrieveUserAttributes retrieveUserAttributes = new RetrieveUserAttributes();
		retrieveUserAttributes.getUserBasicAttributes("ykyuen", retrieveUserAttributes.getLdapContext());
	}

	public LdapContext getLdapContext(){
		LdapContext ctx = null;
		try{
			Hashtable env = new Hashtable();
			env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.ldap.LdapCtxFactory");
			env.put(Context.SECURITY_AUTHENTICATION, "Simple");
			env.put(Context.SECURITY_PRINCIPAL, "administrator@cecid03server.hku.hk");
			env.put(Context.SECURITY_CREDENTIALS, "your password here");
			env.put(Context.PROVIDER_URL, "ldap://cecid-03server:389");
			ctx = new InitialLdapContext(env, null);
			System.out.println("Connection Successful.");
		}catch(NamingException nex){
			System.out.println("LDAP Connection: FAILED");
			nex.printStackTrace();
		}
		return ctx;
	}

	private void getUserBasicAttributes(String username, LdapContext ctx) {
		try {
			SearchControls constraints = new SearchControls();
			constraints.setSearchScope(SearchControls.SUBTREE_SCOPE);
			String[] attrIDs = { "distinguishedName", "sn", "givenname", "mail", "telephonenumber"};
			constraints.setReturningAttributes(attrIDs);
			//First input parameter is search bas, it can be "CN=Users,DC=YourDomain,DC=com"
			//Second Attribute can be uid=username
			NamingEnumeration answer = ctx.search("DC=cecid03server,DC=hku,DC=hk", "sAMAccountName=" + username, constraints);
			if (answer.hasMore()) {
				Attributes attrs = ((SearchResult) answer.next()).getAttributes();
				System.out.println(attrs.get("distinguishedName"));
				System.out.println(attrs.get("givenname"));
				System.out.println(attrs.get("sn"));
				System.out.println(attrs.get("mail"));
				System.out.println(attrs.get("telephonenumber"));
			}else{
				throw new Exception("Invalid User");
			}
		} catch (Exception ex) {
			ex.printStackTrace();
		}
		return;
	}
}

System.out

Connection Successful.
distinguishedName: CN=Kit Yuen,CN=Users,DC=cecid03server,DC=hku,DC=hk
givenName: Ying Kit
sn: Yuen
mail: ykyuen2@cecid.hku.hk
telephoneNumber: 12345678

Done =)

Reference: Retrieve Basic User Attributes from Active Directory using LDAP in Java