从java中的各个位构造一个字节

Question

我正在编写一个随机数生成器,它生成一个伪随机int,然后返回一个int,表示int值中的最低有效位.

public class RNG {

    //algorithm input: first input is the seed
    private int x;

    //primes for calculating next random number
    private int p;
    private int q;

    //constructor
    public RNG()
    {
        p = getPrime();
        q = getPrime();

        //make sure p and q are not equal
        while(p == q)
        {
            q = getPrime();
        }

        //seed must not be divisible by p or q
        //easiest way is to make the seed another prime number
        //this prime does not need to be congruent to 3 mod 4, so
        //getPrime() is not used.

        x = (BigInteger.probablePrime(8, new Random())).intValue();
    }

    //return a pseudorandom prime number using java.util.Random such that
    //the number is congruent to 3 mod 4
    private int getPrime()
    {
        Random rand = new Random();
        int i;
        while(true)
        {
            //generates a random BigInteger. The probability
            //this BigInteger is composite is less than 2^-100
            //bitLength is 8 so maximum prime value is 251
            i = (BigInteger.probablePrime(8, rand)).intValue();
            if((i % 4) == (3 % 4))
            {
                break;
            }
        }

        return i;
    }

    public int next()
    {
        //calculate next algorithm input
        int next = (x * x) % (p * q);

        //set algorithm input for next next() call
        x = next;

        //return least significant bit
        return next & 1;
    }
}

该程序的目的是能够创建一个返回值,然后测试类可以写入文件,并且因为输出是随机生成的数字的最低有效位,所以输出将是加密安全的.

但是,当试图提出测试类的实现时,我无法弄清楚如何处理输出.我需要测试类能够做的是将512位写入输出文件.但是,FileOuputStream类只能将字节写入输出文件.

我想要做的是弄清楚是否有办法将我的随机数生成器中的单个1或0输出分组为字节值,但到目前为止我还没有找到Java支持的任何内容.

Answer 1

您可以使用<<运算符(或位移和赋值运算符<<=)使用位移来构造字节(或整数或长整数)

byte b = 0;
for (int i = 0; i < 8; i++) {
    b <<= 1;
    b |= rng.next();
}