What will be the output of the following Java program?

class output
{
    public static void main(String args[])
    { 
       StringBuffer s1 = new StringBuffer("Hello");
       StringBuffer s2 = s1.reverse();
       System.out.println(s2);
    }
}

Which class is used to read data from the keyboard in Java?

A. Scanner

B. FileReader

C. BufferedReader

D. InputStream

What is the purpose of the `System.out.println()` method in Java?

A. It performs mathematical operations

B. It writes data to a file

C. It reads data from the keyboard

D. It prints data to the standard output stream followed by a newline

Which method is used to write data to a file in Java?

A. read()

B. print()

C. write()

D. scan()

How can you close a file after reading or writing in Java?

A. By using the `terminate()` method

B. By using the `close()` method of the file stream

C. By using the `readLine()` method

D. By using the `exit()` method