如何在 Java 中生成 min 和 max 之间的随机整数？
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How do I generate a random integer between min and max in Java?
提问by David
What method returns a random int between a min and max? Or does no such method exist?
什么方法返回最小值和最大值之间的随机整数？或者不存在这样的方法？
What I'm looking for is something like this:
我正在寻找的是这样的：
NAMEOFMETHOD (min, max)
(where min and max are ints), that returns something like this:
（其中 min 和 max 是ints），返回如下内容：
8
(randomly)
（随机）
If such a method does exist could you please link to the relevant documentation with your answer.
如果确实存在这种方法，请您将答案链接到相关文档。
Thanks.
谢谢。
UPDATE
更新
Attempting to implement the full solution and I get the following error message:
尝试实施完整的解决方案，我收到以下错误消息：
class TestR
{
public static void main (String[]arg)
{
Random random = new Random() ;
int randomNumber = random.nextInt(5) + 2;
System.out.println (randomNumber) ;
}
}
I'm still getting the same errors from the compiler:
我仍然从编译器收到相同的错误：
TestR.java:5: cannot find symbol
symbol : class Random
location: class TestR
Random random = new Random() ;
^
TestR.java:5: cannot find symbol
symbol : class Random
location: class TestR
Random random = new Random() ;
^
TestR.java:6: operator + cannot be applied to Random.nextInt,int
int randomNumber = random.nextInt(5) + 2;
^
TestR.java:6: incompatible types
found : <nulltype>
required: int
int randomNumber = random.nextInt(5) + 2;
^
4 errors
What's going wrong here?
这里出了什么问题？
采纳答案by Mark Byers
Construct a Random object at application startup:
在应用程序启动时构造一个 Random 对象：
Random random = new Random();
Then use Random.nextInt(int):
然后使用Random.nextInt(int)：
int randomNumber = random.nextInt(max + 1 - min) + min;
Note that the both lower and upper limits are inclusive.
请注意，下限和上限均包括在内。
回答by MAK
You can use Random.nextInt(n). This returns a random int in [0,n). Just using max-min+1 in place of n and adding min to the answer will give a value in the desired range.
您可以使用Random.nextInt(n)。这将返回 [0,n) 中的随机整数。只需使用 max-min+1 代替 n 并将 min 添加到答案中就会给出所需范围内的值。
回答by darlinton
import java.util.Random;
导入 java.util.Random;
回答by julius.kabugu
This generates a random integer of size psize
这会生成一个大小为 psize 的随机整数
public static Integer getRandom(Integer pSize) {
if(pSize<=0) {
return null;
}
Double min_d = Math.pow(10, pSize.doubleValue()-1D);
Double max_d = (Math.pow(10, (pSize).doubleValue()))-1D;
int min = min_d.intValue();
int max = max_d.intValue();
return RAND.nextInt(max-min) + min;
}
回答by Jupiter Kasparov
public static int random_int(int Min, int Max)
{
return (int) (Math.random()*(Max-Min))+Min;
}
random_int(5, 9); // For example
回答by kerouac
Using the Random class is the way to go as suggested in the accepted answer, but here is a less straight-forward correct way of doing it if you didn't want to create a new Random object :
按照已接受的答案中的建议，使用 Random 类是一种方法，但如果您不想创建新的 Random 对象，这里有一种不太直接的正确方法：
min + (int) (Math.random() * (max - min + 1));
回答by arcuri82
As the solutions above do not consider the possible overflow of doing max-minwhen minis negative, here another solution (similar to the one of kerouac)
由于上面的解决方案没有考虑 do max-minwhenmin为负的可能溢出，这里是另一种解决方案（类似于 kerouac 的解决方案）
public static int getRandom(int min, int max) {
if (min > max) {
throw new IllegalArgumentException("Min " + min + " greater than max " + max);
}
return (int) ( (long) min + Math.random() * ((long)max - min + 1));
}
this works even if you call it with:
即使您使用以下命令调用它，这也有效：
getRandom(Integer.MIN_VALUE, Integer.MAX_VALUE)
回答by palacsint
With Java 7 or above you could use
使用 Java 7 或更高版本，您可以使用
ThreadLocalRandom.current().nextInt(int origin, int bound)
Javadoc: ThreadLocalRandom.nextInt
Javadoc：ThreadLocalRandom.nextInt
