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
在尝试1中进行以下更改应该可以完成工作-
randomNum = minimum + (int)(Math.random() * (maximum - minimum) );
检查此项以获取工作代码。
其他回答
我认为这段代码会奏效。请尝试一下：
import java.util.Random;
public final class RandomNumber {
public static final void main(String... aArgs) {
log("Generating 10 random integers in range 1..10.");
int START = 1;
int END = 10;
Random randomGenerator = new Random();
for (int idx=1; idx<=10; ++idx) {
// int randomInt=randomGenerator.nextInt(100);
// log("Generated : " + randomInt);
showRandomInteger(START,END,randomGenerator);
}
log("Done");
}
private static void log(String aMessage) {
System.out.println(aMessage);
}
private static void showRandomInteger(int aStart, int aEnd, Random aRandom) {
if (aStart > aEnd) {
throw new IllegalArgumentException("Start cannot exceed End.");
}
long range = (long)aEnd - (long)aStart + 1;
long fraction = (long) (range * aRandom.nextDouble());
int randomNumber = (int) (fraction + aStart);
log("Generated" + randomNumber);
}
}
这将生成范围（最小值-最大值）不重复的随机数列表。
generateRandomListNoDuplicate(1000, 8000, 500);
添加此方法。
private void generateRandomListNoDuplicate(int min, int max, int totalNoRequired) {
Random rng = new Random();
Set<Integer> generatedList = new LinkedHashSet<>();
while (generatedList.size() < totalNoRequired) {
Integer radnomInt = rng.nextInt(max - min + 1) + min;
generatedList.add(radnomInt);
}
}
希望这对你有所帮助。
下面是一个简单的示例，它显示了如何从闭合的[min，max]范围生成随机数，而min<=max为真
您可以将其作为孔中字段类重用，也可以将所有Random.class方法放在一个位置
结果示例：
RandomUtils random = new RandomUtils();
random.nextInt(0, 0); // returns 0
random.nextInt(10, 10); // returns 10
random.nextInt(-10, 10); // returns numbers from -10 to 10 (-10, -9....9, 10)
random.nextInt(10, -10); // throws assert
来源：
import junit.framework.Assert;
import java.util.Random;
public class RandomUtils extends Random {
/**
* @param min generated value. Can't be > then max
* @param max generated value
* @return values in closed range [min, max].
*/
public int nextInt(int min, int max) {
Assert.assertFalse("min can't be > then max; values:[" + min + ", " + max + "]", min > max);
if (min == max) {
return max;
}
return nextInt(max - min + 1) + min;
}
}
另一种选择是使用Apache Commons：
import org.apache.commons.math.random.RandomData;
import org.apache.commons.math.random.RandomDataImpl;
public void method() {
RandomData randomData = new RandomDataImpl();
int number = randomData.nextInt(5, 10);
// ...
}
import java.util.Random;
public class RandomSSNTest {
public static void main(String args[]) {
generateDummySSNNumber();
}
//831-33-6049
public static void generateDummySSNNumber() {
Random random = new Random();
int id1 = random.nextInt(1000);//3
int id2 = random.nextInt(100);//2
int id3 = random.nextInt(10000);//4
System.out.print((id1+"-"+id2+"-"+id3));
}
}
您也可以使用
import java.util.concurrent.ThreadLocalRandom;
Random random = ThreadLocalRandom.current();
然而，这个类在多线程环境中表现不佳。
