Chapter 11, Problem 21E

Explanation of Solution

Method “pariCounts()” to return the number of occurrences of the pairs of letters:

//Import required packages

import java.util.*;

import java.io.*;

//Definition of class Vocabulary

public class Vocabulary

{

    //Definition of main method

    public static void main(String[] args)

    throws FileNotFoundException

    {

        //Create an array list

ArrayList<String> listName=new ArrayList<String>();

        //Add the values to the list

        listName.add("banana");

        listName.add("bends");   

        listName.add("i");   

        listName.add("mend"); 

        listName.add("sandy"); 

        //Call the method pairCounts

        System.out.println(pairCounts(listName));

    }

    //Definition of method pariCounts

public static Map<String, Integer> pairCounts(List<String> list)

    {

        //Create a map

        Map<String, Integer> map = new TreeMap<>();

        //Traverse the for loop to refer the list

        for (String s : list)

        {

            //Set the letters to the varaible "s"

            s = s...