检查String是否仅包含字母

import java.util.regex.Pattern;

public class StringCheck {
    public static boolean isOnlyLetters(String str) {
        // 正则表达式匹配字母
        String pattern = "^[a-zA-Z]+$";
        return Pattern.matches(pattern, str);
    }

    public static void main(String[] args) {
        String str1 = "HelloWorld";
        String str2 = "Hello123";
        System.out.println(isOnlyLetters(str1)); // 输出 true
        System.out.println(isOnlyLetters(str2)); // 输出 false
    }
}

public class StringCheck {
    public static boolean isOnlyLetters(String str) {
        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);
            if (!Character.isLetter(c)) {
                return false;
            }
        }
        return true;
    }

    public static void main(String[] args) {
        String str1 = "HelloWorld";
        String str2 = "Hello123";
        System.out.println(isOnlyLetters(str1)); // 输出 true
        System.out.println(isOnlyLetters(str2)); // 输出 false
    }
}