错误说明它不能将字符串转换为int

public class Main {
    public static void main(String[] args) {
        String str = "12345";
        if (str.matches("\\d+")) {  // "\\d+" 检查字符串是否只包含数字
            int number = Integer.parseInt(str);
            System.out.println("转换成功: " + number);
        } else {
            System.out.println("转换失败: 字符串包含非数字字符");
        }
    }
}

public class Main {
    public static void main(String[] args) {
        String str = "123abc";
        try {
            int number = Integer.parseInt(str);
            System.out.println("转换成功: " + number);
        } catch (NumberFormatException e) {
            System.out.println("转换失败: " + e.getMessage());
        }
    }
}

import java.util.Optional;

public class Main {
    public static Optional<Integer> safeStringToInt(String str) {
        try {
            return Optional.of(Integer.parseInt(str));
        } catch (NumberFormatException e) {
            return Optional.empty();
        }
    }

    public static void main(String[] args) {
        String str = "123abc";
        Optional<Integer> result = safeStringToInt(str);
        result.ifPresentOrElse(
            number -> System.out.println("转换成功: " + number),
            () -> System.out.println("转换失败: 输入不是有效的整数")
        );
    }
}