如何在特定范围内生成随机int值？
以下方法存在与整数溢出相关的错误：
randomNum = minimum + (int)(Math.random() * maximum);
// Bug: `randomNum` can be bigger than `maximum`.
Random rn = new Random();
int n = maximum - minimum + 1;
int i = rn.nextInt() % n;
randomNum = minimum + i;
// Bug: `randomNum` can be smaller than `minimum`.
当前回答
以下代码生成100000到900000之间的随机数。此代码将生成六位数的值。我用这个代码生成一个六位数的OTP。
使用importjava.util.Random来使用此随机方法。
import java.util.Random;
// Six digits random number generation for OTP
Random rnd = new Random();
long longregisterOTP = 100000 + rnd.nextInt(900000);
System.out.println(longregisterOTP);
其他回答
可以使用以下代码：
ThreadLocalRandom.current().nextInt(rangeStart, rangeEndExclusive)
一般使用java.utilforRandom。
您可以定义最小和最大范围以获得这些结果。
Random rand=new Random();
rand.nextInt((max+1) - min) + min;
有一个图书馆在https://sourceforge.net/projects/stochunit/用于处理范围的选择。
StochIntegerSelector randomIntegerSelector = new StochIntegerSelector();
randomIntegerSelector.setMin(-1);
randomIntegerSelector.setMax(1);
Integer selectInteger = randomIntegerSelector.selectInteger();
它具有边缘包含/排除。
int func(int max, int min){
int range = max - min + 1;
// Math.random() function will return a random no between [0.0,1.0).
int res = (int) ( Math.random()*range)+min;
return res;
}
我发现这个例子生成随机数：
此示例生成特定范围内的随机整数。
import java.util.Random;
/** Generate random integers in a certain range. */
public final class RandomRange {
public static final void main(String... aArgs){
log("Generating random integers in the range 1..10.");
int START = 1;
int END = 10;
Random random = new Random();
for (int idx = 1; idx <= 10; ++idx){
showRandomInteger(START, END, random);
}
log("Done.");
}
private static void showRandomInteger(int aStart, int aEnd, Random aRandom){
if ( aStart > aEnd ) {
throw new IllegalArgumentException("Start cannot exceed End.");
}
//get the range, casting to long to avoid overflow problems
long range = (long)aEnd - (long)aStart + 1;
// compute a fraction of the range, 0 <= frac < range
long fraction = (long)(range * aRandom.nextDouble());
int randomNumber = (int)(fraction + aStart);
log("Generated : " + randomNumber);
}
private static void log(String aMessage){
System.out.println(aMessage);
}
}
此类的示例运行：
Generating random integers in the range 1..10.
Generated : 9
Generated : 3
Generated : 3
Generated : 9
Generated : 4
Generated : 1
Generated : 3
Generated : 9
Generated : 10
Generated : 10
Done.
