Question

我正在使用IntelliJ Idea进行编码课程，我决定制作一个有趣的项目。这是我的代码。请注意，java.util.Random已导入：

                <cfset myarray=ArrayNew(1)>
                <cfset counter = 1>
                <cfloop list="#url.TableName#" index="y">

                <cfquery name="findgreatest" dbtype ="query">
                SELECT max(arn) as recno from qSort
                WHERE tbl = '#y#'
                </cfquery>


                <cfset nextTBRC[counter] = ["#findgreatest.recno#"]>



                <cfset counter = counter + 1>


                </cfloop>
                <cfoutput>
                <cfset myvar = "#nextTBRC[2]#">     
                <div>#myvar#</div>
                </cfoutput>

printTrees只是以您在屏幕截图中看到的方式打印出数组输入。输出通常如下所示：

我的代码应该基本上生成一种森林，树木是Ts，下半部分应该是镜像上半部分。然而，下半部分完全是Ts。我如何解决这个问题，以便下半部分是与上半部相似的模式随机，只能逆转？

Answer 1

正如评论中的@SeanVanGorder所示，您经常点击IllegalArgumentException个案，因此您总是为“随机”值选择零。（Sounds like an xkcd comic）。

try / catch块中唯一会抛出此异常的是对Random.nextInt(int)的调用，如果参数不为正，则documented抛出IllegalArgumentException。因此，您的参数Math.abs((int) Math.round(randBounds))不是正面的。

它不是正面的原因是它变为零。很容易理解为什么：

从150开始
你将它除以1.07二十六次
你将它乘以1.07二十四次
因此，在执行randBounds循环的所有50次迭代后，for(int q = 0;q<50;q++){...}的值为150 / 1.07 ^ 26*1.07^24 = 150 * 0.873 = 131
然后将randBounds除以1.05，使其变为150 * 0.873 / 1.05 = 150 * 0.831 = 124.7，并再次重复这些分区/多重放映26次（外循环的迭代）。在这26次迭代结束时，randBounds仅为1.25。
然后重复内循环（使randBounds每次迭代的大小为0.873倍，但现在乘以 1.05而不是除以1.05。但整体变化每次迭代到randBounds为0.873 * 1.05 = 0.917，即你的数量仍在减小。

从1.25开始并将幅度减小0.917倍，经过10次迭代后你将降到0.5以下。因此，一旦完成外循环的36次迭代，randBounds小于1，您将始终获得IllegalArgumentException。

然而，一旦0.5 <= randBounds < 1.5开始，你就会开始变为零，因为它会变为1，而Random.nextInt(1)总是会返回零。所以，实际上，你将开始比36迭代标记更早得到所有零。实际上，这发生在外循环的25次迭代之后。

很难建议修复，因为不清楚正确的行为是什么;唯一的一般修复是识别未检查的异常（如IllegalArgumentException）不应被捕获和吞噬，因为它们表示编程错误。

Answer 2

或许高斯分布会更符合您的喜好：

import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.Validate;

import java.util.Random;

public class StackOverflow45044823 {

  public static void populateField(final char[][] field) {
    Validate.noNullElements(field);
    final Random random = new Random();
    for (int rowNumber = 0; rowNumber < field.length; rowNumber++) {
      for (int columnNumber = 0; columnNumber < field[rowNumber].length; columnNumber++) {
        //random.nextGaussian() / 6.0 =  stdev=1/6 center=0
        //rowNumber / (float) field.length - 0.5 = grows uniformly from -0.5 to 0.5
        if (random.nextGaussian() / 6.0 < rowNumber / (float) field.length - 0.5) {
          field[rowNumber][columnNumber] = 'T';
        } else {
          field[rowNumber][columnNumber] = ' ';
        }
      }
    }
  }

  public static void main(String[] args) {
    final char[][] treeField = new char[50][50];
    populateField(treeField);
    printField(treeField);
  }

  private static void printField(char[][] field) {
    Validate.noNullElements(field);
    for (char[] aField : field) {
      System.out.println(StringUtils.join(aField, '|'));
    }
  }
}

它会产生类似......

的东西

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 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 
 | | | | | | |T| | | | | | | | | | | | | | | | | | | |T| | | | | | | | | | | | | | | | | | | | | | 
 | | | | | | | | | | | | | | | | | | | | | | |T| | | | | | | | | | | | | | | | | | | | | | | | | | 
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为什么我的随机数只返回0？

2 个答案: