Question

我正在尝试将一些Javascript代码移植到Java。我已经成功移植了代码，但它无效 - 每次都在最后一个数字处失败。

检查验证的链接：http://imei-number.com/imei-validation-check/

这是我的Javascript代码：

function imei_gen() {
    var pos;
    var str = new Array(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0);
    var sum = 0;
    var final_digit = 0;
    var t = 0;
    var len_offset = 0;
    var len = 15;
    var issuer;
    var rbi = ["01", "10", "30", "33", "35", "44", "45", "49", "50", "51", "52", "53", "54", "86", "91", "98", "99"];
    var arr = rbi[Math.floor(Math.random() * rbi.length)].split("");
    str[0] = Number(arr[0]);
    str[1] = Number(arr[1]);
    pos = 2;
    while (pos < len - 1) {
        str[pos++] = Math.floor(Math.random() * 10);
    }
    len_offset = (len + 1) % 2;
    for (pos = 0; pos < len - 1; pos++) {
        if ((pos + len_offset) % 2) {
            t = str[pos] * 2;
            if (t > 9) {
                t -= 9;
            }
            sum += t;
        } else {
            sum += str[pos];
        }
    }
    final_digit = (10 - (sum));
    str[len - 1] = final_digit;
    t = str.join('');
    t = t.substr(0, len);
    return t;
}
print(imei_gen());

我使用过ScriptEngine，但是花了太多时间，差不多有2秒钟就完成了。

以下是实施：

import java.io.FileReader;

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;

public class SriptEngineJava {
public static void main(String args[]){
     ScriptEngineManager manager = new ScriptEngineManager();
        ScriptEngine engine = manager.getEngineByName("js");
        try {
          FileReader reader = new FileReader("imei.js");
          engine.eval(reader);
          //reader.close();
        } catch (Exception e) {
          e.printStackTrace();
        }
}
}

最后是Java实现：

public class Imei {

        public static void main(String[] args) {
            Imei.imei_gen();
        }
        public static void imei_gen(){
             int pos;
                int str[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
                int sum = 0;
                int final_digit = 0;
                int t = 0;
                int len_offset = 0;
                int len = 15;
                int issuer;
                String rbi[] = {"01","10","30","33","35","44","45","49","50","51","52","53","54","86","91","98","99"};
                String arr[] = rbi[(int) Math.floor(Math.random() * rbi.length)].split("");
                str[0] = Integer.parseInt(arr[0]);
                str[1] = Integer.parseInt(arr[1]);
                pos = 2;

                while (pos < len - 1) {
                    str[pos++] = (int) (Math.floor(Math.random() * 10) % 10);
                }

                len_offset = (len + 1) % 2;
                for (pos = 0; pos < len - 1; pos++) {

                    if (((pos + len_offset) % 2)==0) {
                        t = str[pos] * 2;
                        if (t > 9) {
                            t -= 9;
                        }
                        sum += t;
                    }
                    else {
                        sum += str[pos];
                    }
                }
                final_digit = (10 - (sum % 10)) % 10;
                str[len - 1] = final_digit;

                String s = "";
                for(int i=0;i<str.length;i++){
                    s += str[i];
                }
                System.out.println(s.substring(0, len));
        }
    }

使用ScriptEngine输出是正确的，但只使用Java，最后一位数字没有得到正确的值。

请检查此网址以验证，您将了解错误是什么： http://imei-number.com/imei-validation-check/

Answer 1

您可能想要了解Java中Luhn算法的这种实现：

public class luhn {
    /**
    Calculate the Luhn sum of the input number
    @param str number to check
    @return sum calcuted with Luhn algorithm
    **/
    public static int luhnTest(String str){
        int sum=0;
        boolean isEven=false;
        for (int i=str.length();i>0;i--){
            int k=Integer.parseInt(str.substring(i-1,i));
            if(isEven){
                k=k*2;
                if(k/10!=0)
                    k=k/10+k%10;
            }

            isEven=!isEven;
            sum+=k;
        }
        return sum;
    }

    /**
    Return true if the input number is valid according to the Luhn formula
    @param str number to check
    **/
    public static boolean isLuhnValid(String str){
        if (luhnTest(str)%10==0)
            return true;
        return false;   
    }

    /**
    Return the check digit that makes the input number valid according to the Luhn formula
    @param str number to check
    @return calculated check digit
    **/
    public static int getCheckDigit(String str){
        int k=luhnTest(str+"0");
        int i=0;
        if(k%10!=0)
            i=10-k%10;
        return i;
    }

    /**
    Return the input number with check digit appended
    @param str number to make Luhn valid
    @return Luhn valid number
    **/
    public static String getLuhnNumber(String str){
        return str+getCheckDigit(str);
    }
}

来源：https://github.com/nicopi/Luhn-Algorithm

将Javascript IMEI验证器移植到Java

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