A palindrome string is a string whose reversed string is equal to the original string. In this Java program, we will see how to print the smallest and largest palindrome words in a string. Given a word sentence in the form of a string, we need to print the smallest and longest palindrome word among these words.

Example:

Input: Wow madam is driving racecar.

Smallest Palindrome: Wow
Longest Palindrome: racecar
Explanation: The string contains three palindrome words (i.e., madam, Wow, racecar) 
         but the length of racecar is greatest and that of wow is smallest.


Input: "Nitin is a good guy"

Smallest Palindrome: a
Longest Palindrome: Nitin

Approach: 

• The lengthPalindrome() function finds the longest and smallest palindrome words by extracting each word of the string and passing it to the checkPalin() function, and then updating the smallest and longest by comparing it with the length of the original string The answer string of the string, if it is a palindrome.
• checkPalin() function checks if the word is palindrome. It returns true if word is palindrome else returns false. It makes sure that vacant strings aren't counted as palindrome because the user may enter quite one spaces in between or at the start of the string
   

Example:

// Java program to print the smallest and
// longest palindromic word out of the words of a sentence

public class Main {

	// Function to check if a
	// word is palindrome
	public static boolean checkPalin(String word)
	{

		int n = word.length();

		// making the check case
		// case insensitive
		word = word.toLowerCase();

		// loop to check palindrome
		for (int i = 0; i < n; i++, n--)
		{
			if (word.charAt(i) != word.charAt(n - 1))
				return false;
		}

		return true;
	}

	// Determine the smallest and biggest
	// palindromes in a given string
	public static void lengthPalindrome(int temp, String words[])
	{
		
		int count = 0;
		String smallest = "", longest = "";
		
		for (int i = 0; i < temp; i++) {
			
			if (checkPalin(words[i])) {
				count++;
				
				// Initialize smallest and longest
				// when first palindromic word
				// is found
				if (count == 1)
					smallest = longest = words[i];

				// Compare smallest and longest with each
				// palindromic words
				else {
					
					// If length of smallest is greater
					// than next palindromic word then
					// Store that word in smallest
					if (smallest.length()
						> words[i].length())
						smallest = words[i];

					// If length of longest is less
					// than next palindromic word then
					// Store that word in longest
					if (longest.length()
						< words[i].length())
						longest = words[i];
				}
			}
		}

		if (count == 0)
			
			System.out.println("No palindrome found");
		
		else {
			
			System.out.println("Smallest palindrome: "
							+ smallest);
			System.out.println("Biggest palindrome: "
							+ longest);
		}
	}

	public static void main(String[] args)
	{
		
		String string = "Wow Madam is driving racecar";
		String word = "";
		
		String[] words = new String[100];
		int temp = 0;

		// Add extra space after string
		// to get the last word
		string = string + " ";

		for (int i = 0; i < string.length(); i++) {
			
			// Split the string into words
			if (string.charAt(i) != ' ') {
				word = word + string.charAt(i);
			}
			
			else {
				
				// Add word to array words
				words[temp] = word;
				temp++;
				word = "";
			}
		}
		
		System.out.println("Inputted String : " + string);
		lengthPalindrome(temp, words);
	}
}

Output

Inputted String : Wow Madam is driving racecar 
Smallest palindrome: Wow
Biggest palindrome: racecar