Write a program to accept a sentence which may be terminated by either ‘.’, ‘?’ or ‘!’ only. The words may be separated by a single blank space and should be case-insensitive.

Perform the following tasks:
(a) Check if the sentence is a Palindrome Sentence. A sentence is a Palindrome Sentence if, after removing the spaces and punctuation, the letters read the same forward and backward. Example: “Never odd or even.”
(b) Display the first-occurring most frequent word in the sentence (in lowercase). If there is a tie, choose the word that appears first in the sentence and if no words are repeated then print NONE.

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

Example 1
INPUT: No lemon no melon.
OUTPUT:
IT IS A PALINDROME SENTENCE.
MOST FREQUENT WORD: no

Example 2
INPUT: Was it a car or a cat I saw?
OUTPUT:
IT IS A PALINDROME SENTENCE.
MOST FREQUENT WORD: a

Example 3
INPUT: It is a rainy day!
OUTPUT:
IT IS NOT A PALINDROME SENTENCE.
MOST FREQUENT WORD: NONE

Example 4
INPUT: Always be careful#
OUTPUT:
INVALID INPUT

import java.util.Scanner;
class Palindrome{
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        System.out.print("Sentence: ");
        String s = in.nextLine();
        char last = s.charAt(s.length() - 1);
        if(".?!".indexOf(last) == -1){
            System.out.println("INVALID INPUT");
            return;
        }
        String str = "";
        int count = 0;
        if(s.length() > 0)
            count = 1;
        for(int i = 0; i < s.length(); i++){
            char ch = s.charAt(i);
            if(ch == ' ')
                count++;
        }
        String a[] = new String[count];
        int f[] = new int[count];
        String word = "";
        int index = 0;
        for(int i = 0; i < s.length(); i++){
            char ch = s.charAt(i);
            if(Character.isLetterOrDigit(ch)){
                str += ch;
                word += ch;
            }
            else{
                a[index++] = word;
                word = "";
            }
        }
        boolean isPalindrome = true;
        for(int i = 0, j = str.length() - 1; i <= j; i++, j--){
            char ch1 = Character.toLowerCase(str.charAt(i));
            char ch2 = Character.toLowerCase(str.charAt(j));
            if(ch1 != ch2){
                isPalindrome = false;
                break;
            }
        }
        if(isPalindrome)
            System.out.println("IT IS A PALINDROME SENTENCE");
        else
            System.out.println("IT IS NOT A PALINDROME SENTENCE");
        int highest = 0;
        for(int i = 0; i < a.length; i++){
            for(int j = 0; j < a.length; j++){
                if(a[i].equalsIgnoreCase(a[j]))
                    f[i]++;
            }
            if(f[i] > highest)
                highest = f[i];
        }
        String most = "";
        for(int i = 0; i < f.length; i++){
            if(f[i] == highest && f[i] > 1){
                most = a[i];
                break;
            }
        }
        if(most.length() > 0)
            System.out.println("MOST FREQUENT WORD: " + most.toLowerCase());
        else
            System.out.println("MOST FREQUENT WORD: NONE");
    }
}