如何让BufferedReader仅读取CSV文件指定行？Java实现案例

我正在为学校项目编写Java程序，读取格式为(date, state, fips code, # of cases, # of deaths)的新冠疫情CSV文本文件数据。该文件包含2021年1月1日至2023年3月23日的每日数据，总计6万余行冗余内容，但我仅需要最后55行的美国各地区累计病例数与死亡数。请问如何让BufferedReader仅读取这最后55行数据？

问题解决更新（2023年5月1日） #

感谢各位解答，我已于昨日自行解决该问题。我通过在while循环中添加判断逻辑，确保仅读取以字符串"2023-03-23"开头的行。

实现代码 #

StateCovidStats类 #

import java.io.*;
import java.util.*;
public class StateCovidStats extends State 
{
    private int cases, deaths;
    
    // 默认构造方法
    public StateCovidStats() 
    {
        
    }
    
    // 带参构造方法
    public StateCovidStats(String theName, int caseCount, int deathCount) 
    {
        super(theName);
        cases=caseCount;
        deaths=deathCount;
    }
    
    public void displayStats() 
    {
        System.out.println("----------------------------------------");
        System.out.println(this.getName()+" Stats:");
        System.out.println("Cases: "+this.getCases());
        System.out.println("Deaths: "+this.getDeaths());
        System.out.println("----------------------------------------");
    }
    
    // Getter方法
    public String getStateName() 
    {
        return this.getName();
    }
    
    public int getCases() 
    {
        return cases;
    }
    
    public int getDeaths() 
    {
        return deaths;
    }
    
    // Setter方法
    public void setStateName(String newName) 
    {
        this.setName(newName);
    }
    
    public void setCases(int caseCount)
    {
        cases=caseCount;
    } 
    
    public void setDeaths(int deathCount) 
    {
        deaths=deathCount;
    }
    
    @Override
    public String toString() 
    {
        String s="";
        s+=this.getStateName()+" Cases: "+this.getCases()+" Deaths: "+this.getDeaths();
        return s;
        
    }
    
    public static String findMaxCases(ArrayList<StateCovidStats> list) 
    {
        
        int greatest=Integer.MIN_VALUE;
        String nameOfMax="";
        for(int i=0;i<list.size();i++) 
        {
            if(list.get(i).getCases()>greatest) {
                greatest=list.get(i).getCases();
                nameOfMax=list.get(i).getName();
            }
                
        }
        
        return nameOfMax;
    }
    
    public static String findMaxDeaths(ArrayList<StateCovidStats> list) 
    {
        
        int greatest=Integer.MIN_VALUE;
        String nameOfMax="";
        for(int i=0;i<list.size();i++) 
        {
            if(list.get(i).getDeaths()>greatest) {
                greatest=list.get(i).getDeaths();
                nameOfMax=list.get(i).getName();
            }
                
        }
        
        return nameOfMax;
    }
    
    public static String findMinCases(ArrayList<StateCovidStats> list) 
    {
        
        int least=Integer.MAX_VALUE;
        String nameOfMin="";
        for(int i=0;i<list.size();i++) 
        {
            if(list.get(i).getCases()<least) {
                least=list.get(i).getCases();
                nameOfMin=list.get(i).getName();
            }
                
        }
        
        return nameOfMin;
    }
    
    public static String findMinDeaths(ArrayList<StateCovidStats> list) 
    {
        
        int least=Integer.MAX_VALUE;
        String nameOfMin="";
        for(int i=0;i<list.size();i++) 
        {
            if(list.get(i).getDeaths()<least) {
                least=list.get(i).getDeaths();
                nameOfMin=list.get(i).getName();
            }
                
        }
        
        return nameOfMin;
    }
    
    
    
    public static void main(String[] args) 
    {
        
        String line="";
        
        long totDeath=0;
        long totCase=0;
        
        ArrayList<StateCovidStats> states=new ArrayList<StateCovidStats>();
        
        try   
        {  
         
        BufferedReader br = new BufferedReader(new FileReader(".\\src\\us-states-Jan-2020-through-March-2023.txt"));  

        
        while ((line = br.readLine()) != null )  
            {
                // 仅处理2023-03-23的数据行
                if(line.startsWith("2023-03-23")) {
                    String[] covid = line.split(",");    // 以逗号为分隔符拆分数据  
                    
                    totDeath+=Integer.parseInt(covid[4]);
                    totCase+=Integer.parseInt(covid[3]);
                    
                    StateCovidStats temp=new StateCovidStats(covid[1],Integer.parseInt(covid[3]),Integer.parseInt(covid[4]));
                    
                    boolean stateExists = false;
                    for(int i=0; i<states.size();i++) 
                    {
                        if(states.get(i).getName().equalsIgnoreCase(temp.getName())) 
                        {
                            stateExists = true;
                            break;
                        }
                    }
                    if(!stateExists) {
                        states.add(temp);
                    }
                }
            } //end of while
        
        
        br.close();
        }   //end of try
        catch (IOException e)   
        {  
        e.printStackTrace();  
        }  //end of catch
        
        // 输出统计结果
        String maxCase=findMaxCases(states);
        String minCase=findMinCases(states);
        String maxDeath=findMaxDeaths(states);
        String minDeath=findMinDeaths(states);
        int maxCaseNum=0;
        int minCaseNum=0;
        int maxDeathNum=0;
        int minDeathNum=0;
        
        for(int i=0; i<states.size();i++) 
        {
            if(states.get(i).getName().equals("New Jersey")) 
            {
                states.get(i).displayStats();
            }
            if(states.get(i).getName().equals(maxCase)) 
            {
                maxCaseNum=states.get(i).getCases();
            }
            
            if(states.get(i).getName().equals(minCase)) 
            {
                 minCaseNum=states.get(i).getCases();
            }
            
            if(states.get(i).getName().equals(maxDeath)) 
            {
                 maxDeathNum=states.get(i).getDeaths();
            }
            
            if(states.get(i).getName().equals(minDeath)) 
            {
                 minDeathNum=states.get(i).getDeaths();
            }
        }
        System.out.println("State With Most Cases: "+maxCase+", "+maxCaseNum+" Cases");
        System.out.println("State With Least Cases: "+minCase+", "+minCaseNum+" Cases");
        System.out.println("State With Most Deaths: "+maxDeath+", "+maxDeathNum+" Deaths");
        System.out.println("State With Least Deaths: "+minDeath+", "+minDeathNum+" Deaths");            
        System.out.println("Total US Cases: "+totCase);
        System.out.println("Total US Deaths: "+totDeath);
        System.out.println("------------------------------------");
        System.out.println("AVG State Cases: "+totCase/55);
        System.out.println("AVG State Deaths: "+totDeath/55);
        
        for(int i=0; i<states.size();i++) 
        {
            if(states.get(i).getName().equals("New Jersey")) 
            {
                states.get(i).displayStats();
            }
        }
    }   //end of main
} //end of class

State类 #

public class State 
{
    private String stateName,timeZone;
    private int population;
    private double density;
    
    // 默认构造方法
    public State()
    {
        
    }
    
    // 带参构造方法
    public State(String theName) 
    {
        stateName=theName;
    }
    
    // 名称的Getter和Setter方法
    public String getName() 
    {
        return stateName;
    }
    
    public void setName(String theName) 
    {
        stateName=theName;
    }
}

内容的提问来源于stack exchange，提问作者Dzubek