Xorshift RNGs生成随机数

private transient int randomSeed;

randomSeed = seedGenerator.nextInt() | 0x0100;

private int randomLevel() {
        int x = randomSeed;
        x ^= x << 13;
        x ^= x >>> 17;
        randomSeed = x ^= x << 5;
        if ((x & 0x80000001) != 0) // test highest and lowest bits
            return 0;
        int level = 1;
        while (((x >>>= 1) & 1) != 0) ++level;
        return level;
    }

 通过异或和位移 , 每次生成不同的32位, 周期为2的32次方减1

 

来自JDK ConcurrentSkipListMap