字符串回文在Java中的应用案例

字符串回文是指一个字符串正着读和反着读都一样的现象

1. 检查字符串是否为回文：

public class PalindromeChecker {
    public static void main(String[] args) {
        String input = "racecar";
        boolean isPalindrome = isPalindrome(input);
        System.out.println("Is the input string a palindrome? " + isPalindrome);
    }

    public static boolean isPalindrome(String input) {
        if (input == null || input.length() == 0) {
            return false;
        }

        int left = 0;
        int right = input.length() - 1;

        while (left < right) {
            if (input.charAt(left) != input.charAt(right)) {
                return false;
            }
            left++;
            right--;
        }

        return true;
    }
}

2. 反转字符串：

public class StringReverser {
    public static void main(String[] args) {
        String input = "hello";
        String reversed = reverse(input);
        System.out.println("Reversed string: " + reversed);
    }

    public static String reverse(String input) {
        if (input == null || input.length() == 0) {
            return input;
        }

        char[] chars = input.toCharArray();
        int left = 0;
        int right = chars.length - 1;

        while (left < right) {
            char temp = chars[left];
            chars[left] = chars[right];
            chars[right] = temp;
            left++;
            right--;
        }

        return new String(chars);
    }
}

3. 回文子串查找：

public class PalindromeSubstringFinder {
    public static void main(String[] args) {
        String input = "babad";
        String longestPalindrome = findLongestPalindrome(input);
        System.out.println("Longest palindrome substring: " + longestPalindrome);
    }

    public static String findLongestPalindrome(String input) {
        if (input == null || input.length() == 0) {
            return "";
        }

        int maxLength = 1;
        int start = 0;

        for (int i = 0; i < input.length(); i++) {
            int len1 = expandAroundCenter(input, i, i);
            int len2 = expandAroundCenter(input, i, i + 1);
            int len = Math.max(len1, len2);

            if (len > maxLength) {
                maxLength = len;
                start = i - (len - 1) / 2;
            }
        }

        return input.substring(start, start + maxLength);
    }

    private static int expandAroundCenter(String input, int left, int right) {
        while (left >= 0 && right < input.length() && input.charAt(left) == input.charAt(right)) {
            left--;
            right++;
        }
        return right - left - 1;
    }
}

这些案例展示了字符串回文在Java中的基本应用，包括检查回文、反转字符串和查找回文子串。你可以根据自己的需求对这些案例进行修改和扩展。