計算年度增長率：

增長率公式: (a-b)b*100+'%'   =》(前面的數字-後面的數字)/後面的數字*100

package cn.demo;

import org.apache.commons.collections.CollectionUtils;
import java.util.ArrayList;
import java.util.List;

/**
 * @author Administrator
 * @date 2020/7/31
 */
public class GrowthRateDemo {
    /**
     * 初始化資料
     * @return
     */
   public static List<PersonInfo>  getPerson(){
 
        List<PersonInfo> list=new ArrayList<>();

        PersonInfo personInfo=new PersonInfo();
        personInfo.setCountNumber(100);
        personInfo.setCreateTime("2016");

        PersonInfo personInfo2=new PersonInfo();
        personInfo2.setCountNumber(450);
        personInfo2.setCreateTime("2017");
 

        PersonInfo personInfo4=new PersonInfo();
        personInfo4.setCountNumber(22);
        personInfo4.setCreateTime("2018");

        PersonInfo personInfo5=new PersonInfo();
        personInfo5.setCountNumber(100);
        personInfo5.setCreateTime("2019");

        PersonInfo personInfo6=new PersonInfo();
 
        personInfo6.setCountNumber(200);
        personInfo6.setCreateTime("2020");

        list.add(personInfo);
        list.add(personInfo2);
        list.add(personInfo4);
        list.add(personInfo5);
        list.add(personInfo6);
        return list;
    }

    /**
     * 計算年度增長率
     * <p>
     *  以年度分組
     *  <p>
     *  增長率: (a-b)b*100+'%'   =》(前面的數字-後面的數字)/後面的數字*100
     */
    public static List<PersonInfo> getAnalysisData(){
        List<PersonInfo> result =new ArrayList<>();
        List<PersonInfo> person2 =new ArrayList<>();
        List<PersonInfo> person0=new ArrayList<>();

        List<PersonInfo> person = getPerson();
        //第1項
        PersonInfo personInfo0 = person.get(0);
        personInfo0.setGrowthRate("0%");
        person0.add(personInfo0);

        //第一項不做比較
        if (CollectionUtils.isNotEmpty(person)){
            for (int i = 1; i < person.size(); i++) {
                PersonInfo  personInfo=new PersonInfo();
                Integer countNumber = person.get(i).getCountNumber();
                Integer countNumber1 = person.get(i - 1).getCountNumber();
                if (countNumber<countNumber1){
                    //如果下個數大於上個數，則增長率 為 正
                    String growthRate=(countNumber1-countNumber)/countNumber*100+"%";
                    personInfo.setGrowthRate(growthRate);
                }else if (countNumber>countNumber1){
                    //如果下個數小於上個數，則增長率 為 負 
                    String growthRate=  (countNumber-countNumber1)/countNumber1*100+"%";
                    personInfo.setGrowthRate("-"+growthRate);
                }else{
                    //如果相等，增長率為 0
                    personInfo.setGrowthRate("0%");
                }
                personInfo.setCountNumber(person.get(i).getCountNumber());
                personInfo.setCreateTime(person.get(i).getCreateTime());
                person2.add(personInfo);
            }
        }
        //list合併
        result.addAll(person0);
        result.addAll(person2);
        return result;
    }


    public static void main(String[] args) {
        List<PersonInfo> analysisData = getAnalysisData();
        if (CollectionUtils.isNotEmpty(analysisData)){
            analysisData.stream().forEach(item->{
                System.out.println("數量:"+item.getCountNumber());
                System.out.println("增長率:"+item.getGrowthRate());
                System.out.println("時間:"+item.getCreateTime());
                System.out.println("*****************************************************");
            });
        }
    }
}