你可以去看看Random类的源码,但是一般都要有一个随机种子。给你贴一个Random的构造方法,你看看: public Random() { this(++seedUniquifier + System.nanoTime()); } private static volatile long seedUniquifier = 8682522807148012L; /** * Creates a new random number generator using a single {@code long} seed. * The seed is the initial value of the internal state of the pseudorandom * number generator which is maintained by method {@link #next}. * * <p>The invocation {@code new Random(seed)} is equivalent to: * <pre> {@code * Random rnd = new Random(); * rnd.setSeed(seed);}</pre> * * @param seed the initial seed * @see #setSeed(long) */ public Random(long seed) { this.seed = new AtomicLong(0L); setSeed(seed); }
就是1-10的随机数
第一次调用该方法时,它将创建一个新的伪随机数生成器,与以下表达式完全相同 new java.util.Random之后,新的伪随机数生成器可用于此方法的所有调用,但不能用于其他地方。
此方法是完全同步的,可允许多个线程使用而不出现错误。但是,如果许多线程需要以极高的速率生成伪随机数,那么这可能会减少每个线程对拥有自己伪随机数生成器的争用。
返回:
大于等于 0.0 且小于 1.0 的伪随机 double 值。
public Random() { this(++seedUniquifier + System.nanoTime()); }
private static volatile long seedUniquifier = 8682522807148012L; /**
* Creates a new random number generator using a single {@code long} seed.
* The seed is the initial value of the internal state of the pseudorandom
* number generator which is maintained by method {@link #next}.
*
* <p>The invocation {@code new Random(seed)} is equivalent to:
* <pre> {@code
* Random rnd = new Random();
* rnd.setSeed(seed);}</pre>
*
* @param seed the initial seed
* @see #setSeed(long)
*/
public Random(long seed) {
this.seed = new AtomicLong(0L);
setSeed(seed);
}