Question

1. Write a program to input a list of names (strings) from the user and store them
in an ArrayList. The input can be terminated by entering the empty string or
by
entering the string “quit”.
2. Add further functionality to your program so that it searches the ArrayList to
find the first string and the last string according to dictionary ordering and
then prints out these strings (names). Do this exercise without sorting the
names in the ArrayList. For example, if the list contains the following names:
Charles Darwin
Albert Einstein
Issac Newton
Tony Hoare
Grace Hopper
Edgar Dijkstra
Ada Lovelace
Charles Babbage
Stephen Hawking
Your program should output:
The first name in the list in alphabetical order is: Ada Lovelace
The last name in the list in alphabetical order is: Tony Hoare
3. Add to your program so that after completing question 2, it sorts the ArrayList
to put all strings (names) in (alphabetical) order and prints them all out in
order.

Answer 1

//TestArrayList.java

import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;

public class TestArrayList {
        public static void main(String[] args) {
                Scanner sc = new Scanner(System.in);
                // creating a list
                ArrayList list = new ArrayList();

                System.out
                                .println("Enter list of names (blank line or quit to terminate)");
                // reading first line of input
                String input = sc.nextLine();
                // looping as long as input is not empty or 'quit'
                while (!input.isEmpty() && !input.equalsIgnoreCase("quit")) {
                        // adding input to list and reading next line
                        list.add(input);
                        input = sc.nextLine();
                }

                // code for question 2 begins here
                // initializing two variables (to store first and last names in
                // alphabetical order) to null
                String first = null, last = null;
                // looping through the list
                for (String name : list) {
                        // if first is null (this is the first value on the list), setting
                        // name as both first and last
                        if (first == null) {
                                first = last = name;
                        } else {
                                // checking if name is alphabetically smaller than first
                                if (name.compareTo(first) < 0) {
                                        // setting name as new first
                                        first = name;
                                }
                                // checking if name is bigger than last
                                if (name.compareTo(last) > 0) {
                                        // setting name as new last
                                        last = name;
                                }
                        }
                }

                // displaying first and last
                System.out
                                .println("The first name in the list in alphabetical order is: "
                                                + first);
                System.out
                                .println("The last name in the list in alphabetical order is: "
                                                + last);

                // code for question 3 begins..
                // sorting list of names alphabetically
                Collections.sort(list);

                // looping and printing sorted list of names
                System.out.println("Sorted list: ");
                for (String name : list) {
                        System.out.println(name);
                }
        }
}

/*OUTPUT*/

Enter list of names (blank line or quit to terminate)
Charles Darwin
Albert Einstein
Issac Newton
Tony Hoare
Grace Hopper
Edgar Dijkstra
Ada Lovelace
Charles Babbage
Stephen Hawking

The first name in the list in alphabetical order is: Ada Lovelace
The last name in the list in alphabetical order is: Tony Hoare
Sorted list: 
Ada Lovelace
Albert Einstein
Charles Babbage
Charles Darwin
Edgar Dijkstra
Grace Hopper
Issac Newton
Stephen Hawking
Tony Hoare