Java在下面的程序中非法启动类型

而不是：

//program to generate otp 
public class OTP
{
    public const int SECRET_LENGTH = 20; //getting error in this line
    private const string
    MSG_SECRETLENGTH = "Secret must be at least 20 bytes";
    MSG_COUNTER_MINVALUE = "Counter min value is 1";

    public OTP()
    {
    }

    private static int[] dd = new int[10] { 0, 2, 4, 6, 8, 1, 3, 5, 7, 9 }; 

    private byte[] secretKey = new byte[SECRET_LENGTH] 
    {
    0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39,
    0x3A, 0x3B, 0x3C, 0x3D, 0x3E, 0x3F, 0x40, 0x41, 0x42, 0x43
    };

    private ulong counter = 0x0000000000000001;

    private static int checksum(int Code_Digits) 
    {
    int d1 = (Code_Digits/1000000) % 10;
    int d2 = (Code_Digits/100000) % 10;
    int d3 = (Code_Digits/10000) % 10;
    int d4 = (Code_Digits/1000) % 10;
    int d5 = (Code_Digits/100) % 10;
    int d6 = (Code_Digits/10) % 10;
    int d7 = Code_Digits % 10;
    return (10 - ((dd[d1]+d2+dd[d3]+d4+dd[d5]+d6+dd[d7]) % 10) ) % 10;
    }


    private static string FormatOTP(byte[] hmac)
    {
    int offset =  hmac[19] & 0xf ;
    int bin_code = (hmac[offset]   & 0x7f) << 24
        | (hmac[offset+1] & 0xff) << 16
        | (hmac[offset+2] & 0xff) <<  8
        | (hmac[offset+3] & 0xff) ;
    int Code_Digits = bin_code % 10000000;
    int csum = checksum(Code_Digits);
    int OTP = Code_Digits * 10 + csum;

    return string.Format("{0:d08}", OTP);
    }

    public byte[] CounterArray
    {
    get
    {
        return BitConverter.GetBytes(counter);
    }

使用：

public const int SECRET_LENGTH = 20;
       ^^^^^
private const string MSG_SECRETLENGTH = "Secret must be at least 20 bytes"; 
MSG_COUNTER_MINVALUE = "Counter min value is 1";

public final int SECRET_LENGTH = 20;
       ^^^^^
private final String MSG_SECRETLENGTH = "Secret must be at least 20 bytes"; 
private final String MSG_COUNTER_MINVALUE = "Counter min value is 1";