一 代码

package idcard;

/**
* @className: CheckIdCard
* @description: 验证身份证是否合法
* @date: 2022/6/1
* @author: cakin
*/
public class CheckIdCard {
    public static void main(String[] args) {
        // 身份证
        String idCard = "421121103208280092";
        char[] idArr = idCard.toCharArray();
        if (idArr.length != 18) {
            System.out.println("身份证号必须是18位");
        }
        // 校验因子
        int[] factors = new int[]{7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2};
        // 模除后的校验码
        String[] mods = new String[]{"1", "0", "X", "9", "8", "7", "6", "5", "4", "3", "2"};
        // 对身份证进行加权求和计算
        int sum = 0;
        for (int i = 0; i < idArr.length - 1; i++) {
            char item = idArr[i];
            int n = item - '0';
            sum += factors[i] * n;
        }

        // 求和数据对11取模
        int mod = sum % 11;

        // 取模后的数和身份证最后以为进行对比
        String last = mods[mod];
        String lastNumber = idArr[idArr.length - 1] + "";
        if (lastNumber.equals(last)) {
            System.out.println("身份证合法");
        } else {
            System.out.println("身份证: " + idCard + " 格式不合法!");
        }
    }
}

二 测试

身份证: 421121103208280092 格式不合法!