Java/strings/Palindrome.java at master · debugmm/Java · GitHub

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package strings;

/** Wikipedia: https://en.wikipedia.org/wiki/Palindrome */

class Palindrome {

/** Driver Code */

public static void main(String[] args) {

String[] palindromes = {null, "", "aba", "123321"};

for (String s : palindromes) {

assert isPalindrome(s) && isPalindromeRecursion(s) && isPalindrome1(s);

}

String[] notPalindromes = {"abb", "abc", "abc123"};

for (String s : notPalindromes) {

assert !isPalindrome(s) && !isPalindromeRecursion(s) && !isPalindrome1(s);

}

/**

* Check if a string is palindrome string or not

* @param s a string to check

* @return {@code true} if given string is palindrome, otherwise {@code false}

public static boolean isPalindrome(String s) {

return (s == null || s.length() <= 1) || s.equals(new StringBuilder(s).reverse().toString());

}

/**

* Check if a string is palindrome string or not using recursion

* @param s a string to check

* @return {@code true} if given string is palindrome, otherwise {@code false}

public static boolean isPalindromeRecursion(String s) {

if (s == null || s.length() <= 1) {

return true;

}

if (s.charAt(0) != s.charAt(s.length() - 1)) {

return false;

}

return isPalindrome(s.substring(1, s.length() - 1));

}

/**

* Check if a string is palindrome string or not another way

* @param s a string to check

* @return {@code true} if given string is palindrome, otherwise {@code false}

public static boolean isPalindrome1(String s) {

if (s == null || s.length() <= 1) {

return true;

}

for (int i = 0, j = s.length() - 1; i < j; ++i, --j) {

if (s.charAt(i) != s.charAt(j)) {

return false;

}

return true;

}

Java/strings/Palindrome.java at master · debugmm/Java · GitHub

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