Java-Coding-Problems/Chapter01/P11_CheckPalindrome/src/modern/challenge/Strings.java at master · learningPartha/Java-Coding-Problems · GitHub

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package modern.challenge;

import java.util.stream.IntStream;

public final class Strings {

    private Strings() {
        throw new AssertionError("Cannot be instantiated");
    }

    public static boolean isPalindromeV1(String str) {

        if (str == null || str.isBlank()) {
            // or throw IllegalArgumentException
            return false;
        }

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

        while (right > left) {

            if (str.charAt(left) != str.charAt(right)) {
                return false;
            }

            left++;
            right--;
        }

        return true;
    }

    public static boolean isPalindromeV2(String str) {

        if (str == null || str.isBlank()) {
            // or throw IllegalArgumentException
            return false;
        }

        int n = str.length();

        for (int i = 0; i < n / 2; i++) {
            if (str.charAt(i) != str.charAt(n - i - 1)) {
                return false;
            }
        }

        return true;
    }

    public static boolean isPalindromeV3(String str) {

        if (str == null || str.isBlank()) {
            // or throw IllegalArgumentException
            return false;
        }

        return str.equals(new StringBuilder(str).reverse().toString());
    }

    public static boolean isPalindromeV4(String str) {

        if (str == null || str.isBlank()) {
            // or throw IllegalArgumentException
            return false;
        }

        return IntStream.range(0, str.length() / 2)
                .noneMatch(p -> str.charAt(p) != str.charAt(str.length() - p - 1));
    }
}