For instance:
var env = new Hashtable<String, String>();
env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.ldap.LdapCtxFactory");
env.put("com.sun.jndi.ldap.connect.timeout", "Foo");
new InitialContext(env);
| Exception java.lang.NumberFormatException: For input string: "Foo"
| at NumberFormatException.forInputString (NumberFormatException.java:68)
| at Integer.parseInt (Integer.java:652)

The LDAP provider is just used as an example here. It seems the DNS provider might have similar issues.