Question

Write an interactive Java class Project8Q3, that will display a menu with the available commands 'G', 'D', and 'X'. If 'G' is selected, prompt the user for the ID of a president to display to the screen and then display the president's information. If 'D' is selected, display all the values in the LinkedHashMap to the user with their associated LinkedHashMap key. If 'X' is selected, exit the program. The class should have the method addPresident(id, lastName, firstName, middleInitial) which stores each president's information from the table above into a custom President object class and then into a LinkedHashMap using the ID of the president for the key. Create a second method showPresidents() that displays all the president's information in each element of the LinkedHashMap. Finally create a third method showPresident() that displays the president's information for the ID entered by the user.

ID Last Name First Name Middle Initial

16 Lincoln Abraham null

18 Grant Ulysses S

26 Roosevelt Theodore null

27 Taft William H

29 Harding Warren G

Answer 1

INPUT
########

It is assumed that input file is in same directory as that of program and input file have an header line as in the screenshot below

//############################ PGM START #########################

import java.io.File;
import java.io.FileNotFoundException;
import java.util.HashMap;
import java.util.Scanner;

public class Project8Q3 {
  
   public static HashMap<String,String> h1=new HashMap<String,String>();
  
   //method to add president record to hashmap
   public static void addPresident(String id,String lastName,String firstName,String middleInitial) {
      
       //if middle inital is null then add empty string
       if(middleInitial=="null") {
           middleInitial="";
       }
       //add id as key and combination of all the names as value
       h1.put(id,(lastName+" "+firstName+" "+middleInitial));
   }
  
   //method to show all the president info
   public static void showPresidents() {
       //for each key in hashmap , print key and its correponsing value
       for (String name: h1.keySet()){
            String key = name.toString();
            String value = h1.get(name).toString();
            System.out.println(key +" " + value);
       }
   }
   //method to print a record based on the id given
   public static void showPresident(String id) {
       //if id exist in hashmap print its value
       if (h1.containsKey(id)) {
            String a = h1.get(id);
            System.out.println("President Name:"+a);
        }else {
           System.out.println("President with the id "+id+" does not exist");
        }
   }
   //main method
   public static void main(String[] args) {
       char choice;
      
       Scanner s=new Scanner(System.in);
       try {
          
           //read the file president.txt
           Scanner file1=new Scanner(new File("president.txt"));
          
           //skipping the header
           if(file1.hasNext())
               file1.nextLine();
          
           //reading line one by one in the file
           while(file1.hasNext()) {
               //split the line based on space and separate each value
               String temp[]=file1.nextLine().split(" ");
               //add the values as one record in hash map
               addPresident(temp[0],temp[1],temp[2],temp[3]);
           }
           file1.close();
          
           //repeat untill user exit
           while(true) {
               System.out.print("__MAIN MENU__\nG. Display president details using ID\n");
               System.out.println("D. Display all president details\nX. Exit\nEnter your choice: ");
               choice=s.nextLine().toUpperCase().charAt(0);
               switch(choice) {
                   case 'G': System.out.print("Enter ID: ");
                               String id=s.nextLine();
                               showPresident(id);
                               break;
                              
                   case 'D':System.out.println("Complete President Info......");
                               showPresidents();  
                               break;
                              
                   case 'X': System.out.println("Exiting.........");
                               System.exit(0);
                               break;
                              
                   default: System.out.println("Wrong choice!!!!!, Please re-enter");
                               break;
               }
               System.out.println();
           }
          
       } catch (FileNotFoundException e) {
           System.out.println("File doesnot exist in the current directory of program");
       }
       s.close();

   }
}

//##################################### PGM END ###############################

OUTPUT
########