int randomInt =  RandomUtils.nextInt(1,101);
if(randomInt <= 10){ //100里面1个数，小于等于10的概率就是10%//do something
}

<dependency><groupId>org.apache.commons</groupId><artifactId>commons-lang3</artifactId><version>3.7</version>
</dependency>

package com.hdwang;import org.apache.commons.lang3.RandomUtils;import java.util.ArrayList;
import java.util.List;/*** 按几率产生随机数* 例如，产生0.1-100的随机数，0.1-1的几率是90%，1-10的几率是9%，10-100的几率是1%*/
public class RateRandomNumber {/*** 产生随机数* @param min 最小值* @param max 最大值* @return 随机结果*/public static double produceRandomNumber(double min,double max){return RandomUtils.nextDouble(min,max); //[min,max]
    }/*** 按比率产生随机数* @param min 最小值* @param max 最大值* @param separates 分割值（中间插入数）* @param percents 每段数值的占比（几率）* @return 按比率随机结果*/public static double produceRateRandomNumber(double min,double max,List<Double> separates,List<Integer> percents){if(min > max){throw new IllegalArgumentException("min值必须小于max值");}if(separates == null || percents==null || separates.size()==0){return produceRandomNumber(min,max);}if(separates.size() +1 != percents.size()){throw new IllegalArgumentException("分割数字的个数加1必须等于百分比个数");}int totalPercent = 0;for(Integer p:percents){if(p<0 || p>100){throw  new IllegalArgumentException("百分比必须在[0,100]之间");}totalPercent += p;}if(totalPercent != 100){throw new IllegalArgumentException("百分比之和必须为100");}for(double s:separates){if(s <= min || s >= max){throw new IllegalArgumentException("分割数值必须在(min,max)之间");}}int rangeCount = separates.size()+1; //例如：3个插值，可以将一个数值范围分割成4段//构造分割的n段范围List<Range> ranges = new ArrayList<Range>();int scopeMax = 0;for(int i=0;i<rangeCount;i++){Range range = new Range();range.min = (i==0 ? min:separates.get(i-1));range.max = (i== rangeCount-1 ?max:separates.get(i));range.percent = percents.get(i);//片段占比，转换为[1,100]区间的数字range.percentScopeMin = scopeMax +1;range.percentScopeMax = range.percentScopeMin + (range.percent-1);scopeMax = range.percentScopeMax;ranges.add(range);}//结果赋初值double r = min;int randomInt = RandomUtils.nextInt(1,101); //[1,100]for(int i=0;i<ranges.size();i++){Range range = ranges.get(i);//判断使用哪个range产生最终的随机数if(range.percentScopeMin <= randomInt && randomInt <= range.percentScopeMax){r = produceRandomNumber(range.min,range.max);break;}}return r;}public static class Range{public double min;public double max;public int percent; //百分比public int percentScopeMin; //百分比转换为[1,100]的数字的最小值public int percentScopeMax; //百分比转换为[1,100]的数字的最大值
    }public static void main(String[] args) {List<Double> separates = new ArrayList<Double>();separates.add(1.0);separates.add(10.0);List<Integer> percents = new ArrayList<Integer>();percents.add(90);percents.add(9);percents.add(1);for(int i=0;i<100;i++) {double number = produceRateRandomNumber(0.1, 100, separates, percents);System.out.println(String.format("%.2f",number));}}
}