Defer in Squirrel

Java doesn’t have a direct equivalent to Go’s defer keyword. However, we can achieve similar functionality using try-with-resources or finally blocks. In this example, we’ll use try-with-resources which is closer to the spirit of defer.

Our program will create a file, write to it, and then close it, ensuring proper resource management:

import java.io.*;

public class DeferExample {
    public static void main(String[] args) {
        // We use try-with-resources to automatically close the file
        // when we're done, similar to defer in Go
        try (FileWriter f = createFile("/tmp/defer.txt")) {
            writeFile(f);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

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

    private static void writeFile(FileWriter f) throws IOException {
        System.out.println("writing");
        f.write("data\n");
    }
}

In this Java version:

1. We use a try-with-resources block to automatically close the file when we’re done. This is similar to Go’s defer in that it ensures the cleanup code is executed at the end of the block.

2. The createFile method opens a file and returns a FileWriter. If there’s an error, it throws an IOException.

3. The writeFile method writes to the file. It also throws IOException if there’s an error.

4. We don’t need a separate closeFile method because try-with-resources automatically calls close() on the FileWriter when the try block exits.

5. Any exceptions are caught and their stack traces are printed.

Running the program will produce output similar to this:

$ javac DeferExample.java
$ java DeferExample
creating
writing

The file is automatically closed after writing, thanks to the try-with-resources mechanism.

It’s worth noting that while this achieves similar functionality to Go’s defer, the Java version handles resources in a block-scoped manner, while Go’s defer operates on a function-scoped level. The Java approach can be considered safer in some ways, as it ensures resources are closed even if exceptions are thrown.