fileCreate.java

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.lang.NumberFormatException;

class AddFriend {

	public static void main(String data[])
	{

		try {

			// Get the name of the contact to be updated
			// from the Command line argument
			String newName = data[0];

			// Get the number to be updated
			// from the Command line argument
			long newNumber = Long.parseLong(data[1]);

			String nameNumberString;
			String name;
			long number;
			int index;

			// Using file pointer creating the file.
			File file = new File("friendsContact.txt");

			if (!file.exists()) {

				// Create a new file if not exists.
				file.createNewFile();
			}

			// Opening file in reading and write mode.

			RandomAccessFile raf
				= new RandomAccessFile(file, "rw");
			boolean found = false;

			// Checking whether the name
			// of contact already exists.
			// getFilePointer() give the current offset
			// value from start of the file.
			while (raf.getFilePointer() < raf.length()) {

				// reading line from the file.
				nameNumberString = raf.readLine();

				// splitting the string to get name and
				// number
				String[] lineSplit
					= nameNumberString.split("!");

				// separating name and number.
				name = lineSplit[0];
				number = Long.parseLong(lineSplit[1]);

				// if condition to find existence of record.
				if (name == newName
					|| number == newNumber) {
					found = true;
					break;
				}
			}

			if (found == false) {

				// Enter the if block when a record
				// is not already present in the file.
				nameNumberString
					= newName + "!"
					+ String.valueOf(newNumber);

				// writeBytes function to write a string
				// as a sequence of bytes.
				raf.writeBytes(nameNumberString);

				// To insert the next record in new line.
				raf.writeBytes(System.lineSeparator());

				// Print the message
				System.out.println(" Friend added. ");

				// Closing the resources.
				raf.close();
			}
			// The contact to be updated
			// could not be found
			else {

				// Closing the resources.
				raf.close();

				// Print the message
				System.out.println(" Input name"
								+ " does not exists. ");
			}
		}

		catch (IOException ioe) {

			System.out.println(ioe);
		}
		catch (NumberFormatException nef) {

			System.out.println(nef);
		}
	}
}