Files.exists() / isFile() / isDirectory() / createDirectory()

// Checks whether a file or directory exists.
Files.exists(Path.of("path"));

// Checks whether the path points to a regular file.
Files.isFile(Path.of("path"));

// Checks whether the path points to a directory.
Files.isDirectory(Path.of("path"));

// Creates a directory, including any missing intermediate directories.
Files.createDirectories(Path.of("path"));

// Deletes a file.
Files.delete(Path.of("path"));

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

Path filePath = Path.of("sample.txt");
Path dirPath  = Path.of("output/data");

// Check whether the file exists.
if (Files.exists(filePath)) {
    System.out.println("The file exists.");
} else {
    System.out.println("The file does not exist.");
}

// Determine whether the path is a file or a directory.
System.out.println(Files.isRegularFile(filePath)); // true if it is a regular file.
System.out.println(Files.isDirectory(dirPath));    // true if it is a directory.

// Create a directory, including any intermediate directories.
try {
    Files.createDirectories(dirPath);
    System.out.println("Directory created.");
} catch (IOException e) {
    e.printStackTrace();
}

// Delete the file.
try {
    Files.deleteIfExists(filePath);
    System.out.println("Deletion complete (does nothing if the file does not exist).");
} catch (IOException e) {
    e.printStackTrace();
}

The "check-then-act" pattern — checking with exists() before performing an operation — is susceptible to a race condition known as TOCTOU (Time-Of-Check Time-Of-Use). In a multithreaded environment, another process may create or delete the file between the check and the operation. It is recommended to handle such cases with exception handling rather than relying on existence checks.

delete() cannot remove a non-empty directory. To delete a directory along with its contents, you need to combine it with Files.walk() and delete recursively.