java 在 Math.random() 上设置种子
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/2836718/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Set seed on Math.random()
提问by Kevin
I need to write some junit tests on Java code that calls Math.random(). I know that I can set the seed if I was instantiating my own Random object to produce repeatable results. Is there a way to do this also for Math.random()?
我需要对调用Math.random(). 我知道如果我正在实例化我自己的 Random 对象以产生可重复的结果，我可以设置种子。有没有办法做到这一点Math.random()？
回答by rsp
The method Math.random()uses a private static field:
该方法Math.random()使用私有静态字段：
private static Random randomNumberGenerator;
If you really reallyneed to set this to a new Random(CONSTANT_SEED)(for instance you need to JUNit test code which you have no control over) you could do so by using reflection.
如果您真的需要将其设置为 a new Random(CONSTANT_SEED)（例如您需要 JUNit 测试您无法控制的代码），您可以使用反射来实现。
回答by Jonathan M Davis
How about creating an instance of Randomyourself and using that instead? Math.random()creates one and uses that, so I don't think that you can mess with its seed. If you create a Randomand use it directly, however, you can set the seed for that when you create it, and/or you can call setSeed()on it later.
创建一个Random自己的实例并使用它怎么样？Math.random()创建一个并使用它，所以我认为你不会弄乱它的种子。Random但是，如果您创建并直接使用它，您可以在创建它时为其设置种子，和/或您可以setSeed()稍后调用它。
回答by iTake
Set it with instance of Random with your seed or just extend the methods to return values you need
使用带有种子的 Random 实例设置它，或者只是扩展方法以返回您需要的值
Field field = Math.class.getDeclaredField("randomNumberGenerator");
field.setAccessible(true);
field.set(null, new Random() {
@Override
public double nextDouble() {
return 1;
}
});
