21.
In Java, how can you check if a file or directory exists using the `File` class?

23.
In Java, what is the purpose of the `File.separator` constant?

24.
What is the difference between character streams and byte streams in Java?

25.
In Java, what is the purpose of the `BufferedWriter` class?

27.
In Java, what is the primary purpose of the `PrintStream` class?

28.
What is the difference between reading and writing character streams in Java?

30.
What is the purpose of the `Console` class in Java?