UnknownHostException

UnknownHostException is a checked exception in Java that indicates a problem with network name resolution. It is thrown when a Java application attempts to resolve a hostname or IP address and the Domain Name System (DNS) server cannot find a corresponding record for the requested name. This typically occurs when the hostname is misspelled, the DNS server is unavailable, or the hostname simply does not exist in the DNS.

This exception is a subclass of java.io.IOException. When an UnknownHostException occurs, it means the system could not determine the IP address associated with the given hostname. Common scenarios leading to this exception include trying to connect to a non-existent website, a server with an incorrect IP address configuration, or network connectivity issues that prevent the DNS lookup from completing.

To handle UnknownHostException, developers typically use try-catch blocks in their Java code. Within the catch block, they can log the error, display an informative message to the user, or attempt alternative network operations. Troubleshooting often involves verifying the spelling of the hostname, checking network connectivity, ensuring DNS servers are properly configured and reachable, and confirming that the target host is indeed active and registered in DNS. In some cases, the issue might be temporary, such as a brief DNS server outage.