Recover in CLIPS

Java makes it possible to *recover* from exceptions using try-catch blocks. This mechanism can stop an exception from crashing the program and allow it to continue execution instead.

An example of where this can be useful: a server wouldn't want to crash if one of the client connections exhibits a critical error. Instead, the server would want to close that connection and continue serving other clients. In fact, this is what Java's `javax.servlet` does by default for HTTP servers.

```java
import java.util.function.Supplier;

public class ExceptionHandling {

    // This method throws an exception
    public static void mayThrow() {
        throw new RuntimeException("a problem");
    }

    public static void main(String[] args) {
        // We use a try-catch block to handle exceptions
        try {
            // This code is wrapped in a Supplier to mimic Go's defer functionality
            Supplier<Void> deferred = () -> {
                try {
                    mayThrow();
                } catch (Exception e) {
                    System.out.println("Recovered. Error:\n " + e.getMessage());
                }
                return null;
            };

            // Execute the deferred code
            deferred.get();
        } catch (Exception e) {
            // This catch block won't be executed in this case
            System.out.println("This won't be printed");
        }

        // This code will run, because the exception was caught
        System.out.println("After mayThrow()");
    }
}

In Java, we use try-catch blocks to handle exceptions. The try block contains the code that might throw an exception, and the catch block handles the exception if it occurs.

In this example, we’ve used a Supplier to mimic Go’s deferred function. The mayThrow() method is called within this supplier, and any exception it throws is caught and handled.

The catch block in the main try-catch statement won’t be executed in this case, because the exception is handled within the supplier.

When you run this program, you’ll see:

$ javac ExceptionHandling.java
$ java ExceptionHandling
Recovered. Error:
 a problem
After mayThrow()

This demonstrates that the program was able to recover from the exception and continue execution.

Defer in CLIPS

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Learn X By Example

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Recover in CLIPS