Write a program to accept a sentence which may be terminated by either ‘.’, ‘?’ or ‘!’ only. The words are to be separated by a single blank space and are in uppercase.

Perform the following tasks:
(a) Check for the validity of the accepted sentence.
(b) Convert the non-palindrome words of the sentence into palindrome words by concatenating the word by its reverse (excluding the last character).
Example: The reverse of the word HELP would be LEH (omitting the last alphabet) and by concatenating both, the new palindrome word is HELPLEH. Thus, the word HELP becomes HELPLEH.
Note: The words which end with repeated alphabets, for example ABB would become ABBA and not ABBBA and XAZZZ becomes XAZZZAX.
Palindrome word: Spells same from either side. Example: DAD, MADAM, etc.
(c) Display the original sentence along with the converted sentence.

Test your program for the following data and some random data:

Example 1
INPUT:
THE BIRD IS FLYING.
OUTPUT:
THE BIRD IS FLYING.
THEHT BIRDRIB ISI FLYINGNIYLF

Example 2
INPUT:
IS THE WATER LEVEL RISING?
OUTPUT:
IS THE WATER LEVEL RISING?
ISI THEHT WATERETAW LEVEL RISINGNISIR

Example 3
INPUT:
THIS MOBILE APP LOOKS FINE.
OUTPUT:
THIS MOBILE APP LOOKS FINE.
THISIHT MOBILELIBOM APPA LOOKSKOOL FINENIF

Example 4
INPUT:
YOU MUST BE CRAZY#
OUTPUT:
INVALID INPUT

import java.util.Scanner;
class Convert{
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        System.out.print("ENTER THE SENTENCE: ");
        String s = in.nextLine().toUpperCase();
        if(!valid(s)){
            System.out.println("INVALID INPUT");
            return;
        }
        String p = "";
        String w = "";
        for(int i = 0; i < s.length(); i++){
            char ch = s.charAt(i);
            if(Character.isLetterOrDigit(ch))
                w += ch;
            else{
                p += toPalindrome(w) + " ";
                w = "";
            }
        }
        System.out.println(s);
        System.out.println(p);
    }
    public static boolean valid(String s){
        char last = s.charAt(s.length() - 1);
        if(".?!".indexOf(last) == -1)
            return false;
        if(s.indexOf("  ") >= 0)
            return false;
        return true;
    }
    public static String toPalindrome(String w){
        int i = 0;
        int j = w.length() - 1;
        while(i < j){
            if(w.charAt(i) == w.charAt(j)){
                i++;
                j--;
            }
            else
                break;
        }
        if(i >= j)
            return w;
        String p = new String(w);
        int index = w.length() - 2;
        while(index - 1 >= 0 && w.charAt(index) == w.charAt(index + 1))
            index--;
        for(i = index; i >= 0; i--)
            p += w.charAt(i);
        return p;
    }
}