- False.  The length of an array is always the value that it is initialized as, in this case 10.

- True.  Just like a variable of type A can hold a B object, an ArrayList of type A can hold B objects.

- 
1) It communicates to anyone looking at the code that this is a variable that will not change.
2) Java will enforce that and won't allow you to change it, avoiding accidentally changing it.

- Returns the String that occurs most frequently in the ArrayList.  O(n^2).

- 
The mystery number is: 0
true
--
The mystery number is: 10
false
--
The mystery number is: 0
true
--

- 
	public void reverseFile(String infile, String outfile) {	
		try {
			ArrayList<String> lines = new ArrayList<String>();
			
			BufferedReader in = new BufferedReader(new FileReader(new File(infile)));
			PrintWriter out = new PrintWriter(new FileOutputStream(outfile));
			
			String line = in.readLine();
			
			// add all the lines in the file to an arraylist
			while( line != null ) {
				lines.add(line);
				line = in.readLine();
			}
			
			// write them to the output file starting from the end
			for( int i = lines.size()-1; i >= 0; i-- ) {
				out.println(lines.get(i);
			}
			
			out.close();
			in.close();
		
		} catch (IOException e) {
			System.out.println("Something bad happened :(");
		}
	}