math.random，只生成0? [英] math.random, only generating a 0?

问题描述

以下代码只产生一个 0 ;-;

The following code is only producing a 0 ;-;

我做错了什么?

public class RockPaperSci {

  public static void main(String[] args) {
    //Rock 1
    //Paper 2
    //Scissors 3
    int croll =1+(int)Math.random()*3-1;
    System.out.println(croll);
  }
}

编辑，另一张海报建议修复它.int croll = 1 + (int) (Math.random() * 4 - 1);

Edit, Another Poster suggested something that fixed it. int croll = 1 + (int) (Math.random() * 4 - 1);

谢谢大家！

推荐答案

您正在使用 Math.random() 说明

You are using Math.random() which states

返回带有正号的 double 值，大于或等于 0.0 且小于 1.0.

Returns a double value with a positive sign, greater than or equal to 0.0 and less than 1.0.

您将结果转换为 int，它返回值的整数部分，即 0.

You are casting the result to an int, which returns the integer part of the value, thus 0.

然后1 + 0 - 1 = 0.

考虑使用 java.util.Random

Random rand = new Random();
System.out.println(rand.nextInt(3) + 1);

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