how can i use random numbers in groovy?

问题:

I use this method:

def getRandomNumber(int num){
    Random random = new Random()
    return random.getRandomDigits(num)
}

when I call it I write println getRandomNumber(4)

but I have an error

No signature of method: java.util.Random.getRandomDigits() is applicable for argument types: (java.lang.Integer) values: [4]

Note: I use this method in another groovy class and it works properly without any error

回答1:

There is no such method as java.util.Random.getRandomDigits.

To get a random number use nextInt:

return random.nextInt(10 ** num)

Also you should create the random object once when your application starts:

Random random = new Random()

You should not create a new random object every time you want a new random number. Doing this destroys the randomness.

回答2:

Generate pseudo random numbers between 1 and an [UPPER_LIMIT]

You can use the following to generate a number between 1 and an upper limit.

Math.abs(new Random().nextInt() % [UPPER_LIMIT]) + 1

Here is a specific example:

Example - Generate pseudo random numbers in the range 1 to 600:

Math.abs(new Random().nextInt() % 600) + 1

This will generate a random number within a range for you. In this case 1-600. You can change the value 600 to anything you need in the range of integers.

---

Generate pseudo random numbers between a [LOWER_LIMIT] and an [UPPER_LIMIT]

If you want to use a lower bound that is not equal to 1 then you can use the following formula.

Math.abs(new Random().nextInt() % ([UPPER_LIMIT] - [LOWER_LIMIT])) + [LOWER_LIMIT]

Here is a specific example:

Example - Generate pseudo random numbers in the range of 40 to 99:

Math.abs( new Random().nextInt() % (99 - 40) ) + 40

This will generate a random number within a range of 40 and 99.

回答3:

Generally, I find RandomUtils (from Apache commons lang) an easier way to generate random numbers than java.util.Random

回答4:

For example, let's say that you want to create a random number between 50 and 60, you can use one of the following methods.

new Random().nextInt()%6 +55

new Random().nextInt()%6 returns a value between -5 and 5. and when you add it to 55 you can get values between 50 and 60

Second method:

Math.abs(new Random().nextInt()%11) +50

Math.abs(new Random().nextInt()%11) creates a value between 0 and 10. Later you can add 50 which in the will give you a value between 50 and 60

回答5:

If you want to generate random numbers in range including '0' , use the following while 'max' is the maximum number in the range.

Random rand = new Random()
random_num = rand.nextInt(max+1)