一、Math.random

1Math.random内部使用java.util.Random实现

2 直接调用Math.random是产生一个[0，1)之间的随机数

public static void testMathRandom() {

System.out.println(Math.random());

System.out.println(Math.random());

}

输出：

0.9758482010371091

0.3419060236681194

二、java.util.Random

1 内部使用线性同余随机数发生器

2 nextInt(int n)取值范围[0，n)

3 nextInt()取值范围2的32次方个所有整数(正数、负数、零)

public static void testUtilRandom() {

long seed = System.nanoTime();

Random rand1 = new Random(seed);

Random rand2 = new Random(seed);

System.out.println(rand1.nextInt(100));

System.out.println(rand2.nextInt(100));

byte[] bytes = new byte[8];

rand1.nextBytes(bytes);

System.out.println(Arrays.toString(bytes));

rand2.nextBytes(bytes);

System.out.println(Arrays.toString(bytes));

}

输出：

70

70

[-25, -12, 30, -111, 123, 6, 11, 121]

[-25, -12, 30, -111, 123, 6, 11, 121]