Java program to convert mobile number pad to characters

This post is about Java program to convert mobile number pad to characters.

Example
=========
Here is an image of mobile phone num pad. For every numbers except 1, there are certain character value associated with that. # is used to separate the letters.

If the user presses 44#44, it should print HH

Logic of the program
================

• A hashmap is used to store the number and its corresponding characters.
• If the user presses the number n times before pressing #, the nth character is selected from the hashmap.
• if n is greater than number of characters, select the character which is at the position (n mod number of characters)

Program
========

The java program is as follows:

import java.util.HashMap;
  
 public class MobilePhoneNumPadToCharacters {
  
        public static void main(String[] args) {
         System.out.println(returnWords("222#2#8")); //CAT
         System.out.println(returnWords("5555#2#888888#2222"));  //JAVA
 }
       
       
        public static String returnWords(String str)
        {
               HashMap<Character, String> mobileNumPad = new HashMap<Character, String>();
               
                mobileNumPad.put('2', "ABC");
                mobileNumPad.put('3', "DEF");
                mobileNumPad.put('4', "GHI");
                mobileNumPad.put('5', "JKL");
                mobileNumPad.put('6', "MNO");
                mobileNumPad.put('7', "PQRS");
                mobileNumPad.put('8', "TUV");
                mobileNumPad.put('9', "WXYZ");
                mobileNumPad.put('0'," ");
  
                String[] tokens = str.split("#");
                String out = "";
               
                for (int i = 0; i < tokens.length; i++)
                {
                    char temp = tokens[i].charAt(0);
                    String getWords = mobileNumPad.get(temp);
                    int length = tokens[i].length();
            
                    if(length>getWords.length())
                    {
                      length = length%getWords.length();
                    }
                   
                    if(length == 0)
                    {
                      length = getWords.length();
                    }
                    out = out+getWords.charAt(length-1);
                   
                }
               
                return out;
        }
 }

Good to Read
===========

1) Linked list implementation in java
2) Binary tree implementation in java
3) Java program to check whether string contains unique characters