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
使用Apache Lang3 Commons
Integer.parseInt(RandomStringUtils.randomNumeric(6, 6));
最小值100000到最大值999999
其他回答
我已经创建了一个方法来获取给定范围内的唯一整数。
/*
* minNum is the minimum possible random number
* maxNum is the maximum possible random number
* numbersNeeded is the quantity of random number required
* the give method provides you with unique random number between min & max range
*/
public static Set<Integer> getUniqueRandomNumbers( int minNum , int maxNum ,int numbersNeeded ){
if(minNum >= maxNum)
throw new IllegalArgumentException("maxNum must be greater than minNum");
if(! (numbersNeeded > (maxNum - minNum + 1) ))
throw new IllegalArgumentException("numberNeeded must be greater then difference b/w (max- min +1)");
Random rng = new Random(); // Ideally just create one instance globally
// Note: use LinkedHashSet to maintain insertion order
Set<Integer> generated = new LinkedHashSet<Integer>();
while (generated.size() < numbersNeeded)
{
Integer next = rng.nextInt((maxNum - minNum) + 1) + minNum;
// As we're adding to a set, this will automatically do a containment check
generated.add(next);
}
return generated;
}
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。
Random random = new Random();
int max = 10;
int min = 3;
int randomNum = random.nextInt(max) % (max - min + 1) + min;
使用Java 8 IntStream和Collections.shuffle的不同方法
import java.util.stream.IntStream;
import java.util.ArrayList;
import java.util.Collections;
public class Main {
public static void main(String[] args) {
IntStream range = IntStream.rangeClosed(5,10);
ArrayList<Integer> ls = new ArrayList<Integer>();
//populate the ArrayList
range.forEach(i -> ls.add(new Integer(i)) );
//perform a random shuffle using the Collections Fisher-Yates shuffle
Collections.shuffle(ls);
System.out.println(ls);
}
}
Scala中的等价项
import scala.util.Random
object RandomRange extends App{
val x = Random.shuffle(5 to 10)
println(x)
}
如果你不想重新发明轮子，这里有一个简单明了的解决方案：
RandomStringUtils.randomNumeric(count); // Where count is the number of digits you want in the random number.
Apache Commons，例如组件Lang中的RandomUtils，提供了许多选项来生成任意格式的随机数。
