Panic in CLIPS

import java.io.File;
import java.io.IOException;

public class ExceptionExample {
    public static void main(String[] args) {
        // We'll use exceptions throughout this site to check for
        // unexpected errors. This is the only program on the
        // site designed to throw an exception.
        throw new RuntimeException("a problem");

        // A common use of exceptions is to abort if a method
        // returns an error that we don't know how to
        // (or want to) handle. Here's an example of
        // throwing an exception if we get an unexpected error when creating a new file.
        // try {
        //     File file = new File("/tmp/file");
        //     if (!file.createNewFile()) {
        //         throw new IOException("Failed to create file");
        //     }
        // } catch (IOException e) {
        //     throw new RuntimeException(e);
        // }
    }
}

Running this program will cause it to throw an exception, print an error message and stack trace, and exit with a non-zero status.

When the first exception in main is thrown, the program exits without reaching the rest of the code. If you’d like to see the program try to create a temp file, comment out the first exception and uncomment the file creation code.

$ java ExceptionExample
Exception in thread "main" java.lang.RuntimeException: a problem
    at ExceptionExample.main(ExceptionExample.java:9)

Note that unlike some languages which use return values for handling of many errors, in Java it is idiomatic to use exceptions for error handling in most cases.

In Java, we use exceptions instead of panics. The throw keyword is used to explicitly throw an exception, which is similar to calling panic in other languages. The try-catch block is used to handle exceptions, allowing for more graceful error handling and recovery.

The RuntimeException used in this example is an unchecked exception in Java, which means it doesn’t need to be explicitly caught or declared. This makes it somewhat similar to a panic in behavior, as it can cause the program to terminate if not caught.