Java——判斷回文

package basic;

import java.util.Scanner;

public class Palindrome{
    public static boolean isPalindrome(String raw){
        String str = "";
        // 只拿raw字符串里的字母，拼接到str里
        for(int i = 0; i < raw.length(); i++){
            char ch = raw.charAt(i);
            if((ch>='a'&&ch<='z')||(ch>='A'&&ch<='Z')){
                str += ch;
            }
        }
        // str字母全部小寫化
        str = str.toLowerCase();
        // 判斷是否為回文
        int end = str.length();
        for(int i = 0; i < end/2; i++){
            if(str.charAt(i) != str.charAt(end-i-1)){
                return false;
            }
        }

        return true;
    }

    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);

        // I prefer pi!
        // A man, a plan, a canal: Panama!
        // Madam, I am Adam.
        System.out.printf("Enter a message: ");
        String str = scanner.nextLine();

        if(isPalindrome(str)){
            System.out.println("Palindrome!");
        }else{
            System.out.println("Not a palindrome!");
        }
    }
}