Introduction to the use of Random class in Java

Introduction to the Random class

(Recommended tutorial: java introductory tutorial)

The Random class is specially used to generate a pseudo-random Number, it has two constructors: one constructor uses the default seed (using the current time as the seed), and the other constructor requires the programmer to explicitly pass in a long integer seed.

The Random class provides more ways to generate various pseudo-random numbers than the random() method of the Math class. It can generate pseudo-random numbers of floating point type, pseudo-random numbers of integer type, and You can specify the range within which random numbers are generated.

Constructor:

public Random()    //int范围内的随机数
public Random(long seed)

Code implementation:

1. Generate a random number.

import java.util.Random;

public class Test01 {
    public static void main(String[] args) {
        // 创建随机数对象
        Random random = new Random();

        // 随机产生一个int范围内的数字
        int num1 = random.nextInt();
        System.out.println(num1);  // 范围为[Integer.MIN_VALUE, Integer.MAX_VALUE]之间的一个整数

        // 如果我要产生[0, 100]之间的整数怎么办
        int num2 = random.nextInt(101);
        System.out.println(num2);  // [0, 100]内的一个整数
        // 注意：nextInt(101)翻译为，下一个int类型的数据是101，表示只能取到100

    }
}

(Video tutorial recommendation: java video tutorial)

2. Generate a random number between [-100, 100]

public class Test02 {
    public static void main(String[] args) {
        // 创建随机数对象
        Random random = new Random();

        // 打印一千个
        for (int i = 0; i < 1000; i++) {
            // 随机控制正负号，-1的0次方为1，-1的1次方为-1
            int fuhao = random.nextInt(2);  // 0或1
            fuhao = (fuhao == 0) ? 1 : -1;

            int num3 = random.nextInt(101) * fuhao;
            System.out.println(num3);
        }
    }
}

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