Question

The text files boynames.txt and girlnames.txt, which are included in the source code for this book, contain lists of the 1,000 most popular boy and girl names in the United States for the year 2005, as compiled by the Social Security Administration.

These are blank-delimited files where the most popular name is listed first, the second most popular name is listed second, and so on to the 1,000th most popular name, which is listed last. Each line consists of the first name followed by a blank

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space followed by the number of registered births in the year using that name. For example, the girlnames.txt file begins with

   Emily 25494
   Emma 22532

This indicates that Emily is the most popular name with 25,494 registered nam- ings, Emma is the second most popular with 22,532, and so on.

Write a program that determines how many names are on both the boys’ and the girls’ list. Use the following algorithm:

• Read each girl name as a String, ignoring the number of namings, and add it to a HashSet object.

• Read each boy name as a String, ignoring the number of namings, and add it to the same HashSet object. If the name is already in the HashSet, then the add method returns false. If you count the number of false returns, then this gives you the number of common namings.

• Add each common name to an ArrayList and output all of the common names from this list before the program exits.

Answer 1

import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.HashSet;

public class CommonNames {
   static HashSet<String> names = new HashSet<String>();
   static ArrayList<String> commonNames = new ArrayList<String>();

   public static void main(String... args) {

       readFile("girlnames.txt"); // read girls names file
       readFile("boynames.txt"); // read boys names file
       printCommanNames(); // print common names in both files

   }

   // Method to read names from file specified
   private static void readFile(String fileName) {

       try {
           FileInputStream fileStream = new FileInputStream(fileName); // file input stream object to read file
           DataInputStream dataInputStream = new DataInputStream(fileStream);
           BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(dataInputStream));
           String line;
           while ((line = bufferedReader.readLine()) != null) { // loop through file to read names
               String[] name = line.split(" "); // split by space to read name and count in array
               if (!names.add(name[0])) // if name is already present in hashset then add to commonNames arraylist
                   commonNames.add(name[0]);
           }
           dataInputStream.close(); // close input stream
       } catch (Exception e) {
           System.err.println("Error: " + e.getMessage()); // print error
       }
   }

   // Method to print common Names
   private static void printCommanNames() {

       System.out.println("Common Names are :");
       for (int i = 0; i < commonNames.size(); i++) { // loop through arraylist to print names

           System.out.println(commonNames.get(i));
       }

   }

}

//Output

Problems Javadoc DeclarationConsole terminated> CommonNames [Java ApplicationCPogram Files Javaljdk1.8.0 601bin javaw.exe(25-Apr-2019, 4:37:4 Common Names are: Emmy Emma