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

public static void main(String[] args) {

    Random ran = new Random();

    int min, max;
    Scanner sc = new Scanner(System.in);
    System.out.println("Enter min range:");
    min = sc.nextInt();
    System.out.println("Enter max range:");
    max = sc.nextInt();
    int num = ran.nextInt(min);
    int num1 = ran.nextInt(max);
    System.out.println("Random Number between given range is " + num1);

}

其他回答

 rand.nextInt((max+1) - min) + min;

Java中的Math.Random类是基于0的。所以,如果你这样写:

Random rand = new Random();
int x = rand.nextInt(10);

x将介于0-9之间(含0-9)。

因此,给定以下25项的数组,生成0(数组的基数)和array.length之间的随机数的代码为:

String[] i = new String[25];
Random rand = new Random();
int index = 0;

index = rand.nextInt( i.length );

由于i.length将返回25,因此nextInt(i.length)将返回0-24之间的数字。另一个选项是Math.Random,其工作方式相同。

index = (int) Math.floor(Math.random() * i.length);

为了更好地理解,请查看论坛帖子Random Intervals(archive.org)。

你可以这样做:

import java.awt.*;
import java.io.*;
import java.util.*;
import java.math.*;

public class Test {

    public static void main(String[] args) {
        int first, second;

        Scanner myScanner = new Scanner(System.in);

        System.out.println("Enter first integer: ");
        int numOne;
        numOne = myScanner.nextInt();
        System.out.println("You have keyed in " + numOne);

        System.out.println("Enter second integer: ");
        int numTwo;
        numTwo = myScanner.nextInt();
        System.out.println("You have keyed in " + numTwo);

        Random generator = new Random();
        int num = (int)(Math.random()*numTwo);
        System.out.println("Random number: " + ((num>numOne)?num:numOne+num));
    }
}
rand.nextInt((max+1) - min) + min;

这很好。

您可以在Java 8中简洁地实现这一点:

Random random = new Random();

int max = 10;
int min = 5;
int totalNumber = 10;

IntStream stream = random.ints(totalNumber, min, max);
stream.forEach(System.out::println);