import com.opencsv.csvreader; import com.opencsv.exceptions.csvvalidationexception; import java.io.filereader; import java.io.ioexception; import java.text.parseexception; import java.text.simpledateformat; import java.util.*; public class stockstatistics { public static void main(string[] args) { string filepath = "stocks.csv"; // 请确保csv文件与此java文件在同一目录下，或提供完整路径 simpledateformat sdf = new simpledateformat("yyyy-mm-dd"); map<string, stockdata> monthlydata = new has