Defer in Fortress

In Java, we don’t have a direct equivalent of the defer keyword. However, we can achieve similar functionality using try-with-resources for resource management or finally blocks for cleanup operations. Here’s how we could implement the same concept:

import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;

public class DeferExample {
    public static void main(String[] args) {
        try (BufferedWriter writer = createFile("/tmp/defer.txt")) {
            writeFile(writer);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static BufferedWriter createFile(String path) throws IOException {
        System.out.println("creating");
        return new BufferedWriter(new FileWriter(path));
    }

    private static void writeFile(BufferedWriter writer) throws IOException {
        System.out.println("writing");
        writer.write("data");
    }
}

In this Java example, we use a try-with-resources statement to ensure that the file is properly closed after we’re done writing to it. This is similar to the defer functionality in the original example.

The createFile method opens a file for writing and returns a BufferedWriter. The writeFile method writes some data to the file.

The try-with-resources statement automatically closes the BufferedWriter when the try block is exited, either normally or due to an exception. This is equivalent to the deferred closeFile call in the original example.

Error handling is built into the try-with-resources mechanism. If an exception occurs while closing the resource, it’s suppressed and the original exception (if any) from the try block is thrown. This handles the error checking that was done in the original closeFile function.

To run this program:

$ javac DeferExample.java
$ java DeferExample
creating
writing

The output confirms that the file is created and written to. The closing of the file is handled automatically by the try-with-resources statement.

This Java implementation provides the same functionality as the original example, ensuring that resources are properly managed and cleaned up, even in the face of errors.