StudentList.java

import java.io.*;
import java.text.*;
import java.util.*;

public class StudentList {
	public static void main(String[] args) {
		// checking Arguments.
		if (args.length != 1) {
			System.out.println(constants.INVALID_MESSAGE);
		} else if (args[0].equals(constants.SHOW_ALL)) {
			System.out.println(constants.LOADED_DATA);
			try {
				BufferedReader bufferreader = readfile(); // read elements of file.
				String studentnames[] = bufferreader.readLine().split(constants.COMMA);
				for (String name : studentnames) {
					System.out.println(name.trim());
				}
				bufferreader.close();
			} catch (Exception e) {
			}
			System.out.println(constants.DATA_LOADED);
		} // finding and printing random names from file.
		else if (args[0].equals(constants.RANDOM_NAME)) {
			System.out.println(constants.LOADED_DATA);
			try {
				BufferedReader bufferreader = readfile();
				String studentnames[] = bufferreader.readLine().split(constants.COMMA);
				int randomindex = new Random().nextInt(studentnames.length); // Random object created
				System.out.println(studentnames[randomindex].trim());
				bufferreader.close();
			} catch (Exception e) {
			}
			System.out.println(constants.DATA_LOADED);
		} // added new elemrnt into the file.
		else if (args[0].contains(constants.PLUS)) {
			System.out.println(constants.LOADED_DATA);
			try {
				BufferedWriter bufferwriter = writefile();
				String name = args[0].substring(1);
				Date date = new Date();
				DateFormat dateFormat = new SimpleDateFormat(constants.DATE);
				String formatdate = dateFormat.format(date);
				bufferwriter.write(constants.COMMA + name + constants.LAST_UPDATE_MESSAGE + formatdate);
				bufferwriter.close();
			} catch (Exception e) {
			}

			System.out.println(constants.DATA_LOADED);
		} // find out the specific word from file.
		else if (args[0].contains(constants.FIND)) {
			System.out.println(constants.LOADED_DATA);
			try {
				BufferedReader bufferreader = readfile();
				String studentnames[] = bufferreader.readLine().split(constants.COMMA);
				String name = args[0].substring(1);
				int countNames = 0;
				for (int index = 0; index < studentnames.length; index++) {
					if (studentnames[index].trim().equals(name)) {
						countNames = countNames + 1;
					}

				}
				bufferreader.close();
			} catch (Exception e) {
			}
			System.out.println(constants.DATA_LOADED);
		} // counting the words.
		else if (args[0].contains(constants.COUNT)) {
			System.out.println(constants.LOADED_DATA);
			try {
				BufferedReader bufferreader = readfile();
				char names[] = bufferreader.readLine().toCharArray();
				System.out.println(names.length + constants.FOUND_MESSAGE);
				bufferreader.close();
			} catch (Exception e) {
			}
			System.out.println(constants.DATA_LOADED);
		} else {
			System.out.println(constants.INVALID_MESSAGE);
		}
	}

	private static BufferedWriter writefile() throws IOException {
		return new BufferedWriter(
				new FileWriter(constants.FILE_NAME, true));
	}

	private static BufferedReader readfile() throws FileNotFoundException {
		return new BufferedReader(
				new InputStreamReader(
						new FileInputStream(constants.FILE_NAME)));
	}
}