Temporary Files And Directories in Mercury

Throughout program execution, we often want to create data that isn’t needed after the program exits. Temporary files and directories are useful for this purpose since they don’t pollute the file system over time.

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;

public class TemporaryFilesAndDirectories {

    private static void check(Exception e) {
        if (e != null) {
            throw new RuntimeException(e);
        }
    }

    public static void main(String[] args) {
        try {
            // The easiest way to create a temporary file is by
            // using Files.createTempFile. It creates a file and
            // returns its path. We provide null as the first argument,
            // so it will create the file in the default temporary-file directory.
            Path tempFile = Files.createTempFile("sample", null);
            System.out.println("Temp file name: " + tempFile);

            // Clean up the file after we're done. The OS is
            // likely to clean up temporary files by itself after
            // some time, but it's good practice to do this
            // explicitly.
            tempFile.toFile().deleteOnExit();

            // We can write some data to the file.
            Files.write(tempFile, new byte[]{1, 2, 3, 4});

            // If we intend to create many temporary files, we may
            // prefer to create a temporary directory.
            // Files.createTempDirectory's arguments are similar to
            // createTempFile's, but it returns a directory path.
            Path tempDir = Files.createTempDirectory("sampledir");
            System.out.println("Temp dir name: " + tempDir);

            tempDir.toFile().deleteOnExit();

            // Now we can synthesize temporary file names by
            // prefixing them with our temporary directory.
            File file1 = new File(tempDir.toFile(), "file1");
            FileOutputStream fos = new FileOutputStream(file1);
            fos.write(new byte[]{1, 2});
            fos.close();

        } catch (IOException e) {
            check(e);
        }
    }
}

To run the program, compile and execute it using javac and java:

$ javac TemporaryFilesAndDirectories.java
$ java TemporaryFilesAndDirectories
Temp file name: /tmp/sample8390855484766997669.tmp
Temp dir name: /tmp/sampledir3083217098454138876

In this Java version, we use the Files class from the java.nio.file package to create temporary files and directories. The createTempFile and createTempDirectory methods are used instead of os.CreateTemp and os.MkdirTemp.

We use deleteOnExit() to ensure that the temporary files and directories are deleted when the JVM exits, which is similar to using defer in the original example.

For writing to files, we use Files.write() for the temporary file and FileOutputStream for the file in the temporary directory.

The check method is implemented as a static method that throws a RuntimeException if an exception is passed to it, similar to the panic in the original code.

Note that Java’s temporary file creation methods automatically use appropriate naming conventions and locations based on the operating system, similar to the behavior in the original example.

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Temporary Files And Directories in Mercury