In Java, how can you check whether a given java.io.File object represents a directory (folder) rather than a regular file?

Introduction / Context:
Java applications frequently need to inspect the file system to decide whether a path is a folder that can contain other entries or a regular file that holds data. The java.io.File class represents both files and directories, so you must use its query methods to distinguish between them. This question asks for the correct way to determine whether a File object points specifically to a directory.

Given Data / Assumptions:

• A File object may refer to a non-existent path, a regular file, or a directory.
• The File API provides boolean methods isFile() and isDirectory().
• We are interested in a safe, non-destructive check that does not modify the file system.
• The Java process has sufficient permissions to query the path.

Concept / Approach:
The File class method boolean isDirectory() returns true if and only if the path exists and is a directory according to the underlying file system. It returns false for regular files and for non-existent paths. This method is designed specifically for distinguishing folders from other entries. Using methods like mkdir() or delete() to infer type is risky because they alter the file system or may fail for reasons unrelated to whether the path is a directory. Therefore, the recommended approach is to call isDirectory() on the File object.

Step-by-Step Solution:
Step 1: Construct a File object for the path you want to test, for example File dir = new File("config").Step 2: Optionally verify existence with dir.exists(), though isDirectory() implicitly checks that as well.Step 3: Call dir.isDirectory() to ask the file system whether this path corresponds to a directory.Step 4: Interpret a true result as meaning that dir represents a folder, and a false result as meaning it is either a regular file or does not exist.Step 5: Use this information to decide whether to list contents with listFiles() or treat the path as a file.

Verification / Alternative check:
You can test this by creating both a file and a directory and then calling isDirectory() on each. The method returns true for the directory and false for the file. Attempting to use mkdir() to detect type would instead try to create a directory and can alter the file system or fail with different error conditions, which is not a reliable test. Official documentation and idiomatic Java code use isDirectory() and isFile() together for safe type checking.

Why Other Options Are Wrong:
Option B misuses isFile(), which checks for regular files, not directories. Option C proposes calling mkdir(), which is a creation method; using its result to infer type can be misleading and may create directories unexpectedly. Option D suggests delete(), which removes entries and is clearly undesirable for a simple type check. Only option A uses the dedicated method intended to check whether a File represents a directory.

Common Pitfalls:
One common pitfall is assuming that if isDirectory() returns false, then the path is definitely a regular file; in reality, the path may not exist at all. Another mistake is relying purely on naming conventions, such as the absence of an extension, which is not a reliable indicator across different operating systems. By consistently using isDirectory() and isFile() and handling the case where neither returns true because the path does not exist, you can write safer, more portable file handling logic.

Final Answer:
Correct answer: Call isDirectory() on the File object to test whether it refers to an existing folder