我在这个问题上很费力,以找到合适的数据类型来使用,但我无法确定在不使用任何第三方库的情况下,哪种方法是最有效和最简单的编程方法:
问题:考虑自 1990 年以来每个月在 CSV 文件中给出的 N 家公司的股价。文件格式如下,第一行作为标题。
Year,Month,Company A, Company B,Company C, .............Company N
1990, Jan, 10, 15, 20, , ..........,50
1990, Feb, 10, 15, 20, , ..........,50
.
.
.
.2013, 9月, 50, 10, 15............500
输出:股价最高的每个公司年度和月份的列表。
我已经考虑过使用树,哈希图,列表,但我无法最终确定一个解决方案。我是Java的新手,到目前为止有几周的Java编码经验。感谢伪代码,程序或使用的数据类型形式的任何帮助。
好的,有无数种方法可以做到这一点,但我最喜欢的一种是创建一个公司类来保存 Company.name、公司.月、公司.年、公司.价格并使用地图添加数据。 然后,添加逻辑将检查地图以查看是否存在具有相同名称的公司,如果不存在或新公司价格更大,只需将新公司数据放入地图中,并将公司名称作为键。 好吧,下面的代码只是为了演示目的,我会使用 eclipse 来生成 getter/setter,并使用它们而不是像演示一样的直接成员变量。 并且此演示缺少从CSV文件中读取和收集公司数据的功能。
公司装载机.java
package org.cnci.poc;
import java.io.File;
import java.io.FileInputStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Scanner;
public class CompanyLoader {
private List<Company> companies;
private int lastReadIdx=0;
public CompanyLoader() {
}
// Simply read the CSV and return the next set of company data
private Company getNextCompanyData() {
if (companies == null) {
lastReadIdx = 0;
try {
loadCompanies();
} catch (Exception e) {
}
}
if (companies == null) return null;
if (lastReadIdx < companies.size()) return companies.get(lastReadIdx++);
return null;
}
public void loadCompanies() throws Exception {
Scanner s = null;
try {
companies = new ArrayList<Company>();
File f = new File("test.csv");
System.out.println(f.getAbsolutePath());
s = new Scanner(new FileInputStream(f));
String[] headers = readLine(s);
System.out.println("headers: " + Arrays.toString(headers));
if (headers != null && headers.length >0) {
String[] data = null;
while ((data = readLine(s)) != null) {
System.out.println("data: " + Arrays.toString(data));
if (data.length != headers.length) {
companies = null;
throw new Exception("Invalid Data - headers count " + headers.length + " does not match with data count "+data.length);
}
String year = data[0];
String month = data[1];
for (int x=2; x<data.length; x++) {
double price = new Double(data[x]).doubleValue();
Company company = new Company(headers[x], year, month, price);
companies.add(company);
}
}
}
} finally {
if (s != null) s.close();
}
}
private String[] readLine(Scanner s) {
if (s.hasNextLine()) {
return s.nextLine().trim().split(",");
}
return null;
}
public void processCompanies() {
Map<String, Company> companies = new HashMap<String, Company>();
Company newCompany = null;
// repeat until all company data processed from CSV file
while ((newCompany = getNextCompanyData()) != null) {
Company oldCompany = companies.get(newCompany.getName());
if (oldCompany == null || newCompany.getPrice() > oldCompany.getPrice())
companies.put(newCompany.getName(), newCompany);
}
// Done, now display the winners
for (String name : companies.keySet()) {
Company company = companies.get(name);
System.out.println(company.getName() + " highest price " + company.getPrice() + " is " + company.getMonth() + " " + company.getYear());
}
}
public static void main(String[] args) {
CompanyLoader loader = new CompanyLoader();
loader.processCompanies();
}
}
公司.java
package org.cnci.poc;
public class Company {
private String name;
private String year;
private String month;
private double price;
public Company(String name, String year, String month, double price) {
super();
this.name = name;
this.year = year;
this.month = month;
this.price = price;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getYear() {
return year;
}
public void setYear(String year) {
this.year = year;
}
public String getMonth() {
return month;
}
public void setMonth(String month) {
this.month = month;
}
public double getPrice() {
return price;
}
public void setPrice(double price) {
this.price = price;
}
@Override
public String toString() {
return "Company [name=" + name + ", year=" + year + ", month=" + month + ", price=" + price + "]";
}
}
测试.csv
Year,Month,Company A,Company B,Company C,Company D,Company N
1990, Jan, 10, 15, 20, 31, 50
1990, Feb, 11, 14, 21, 30, 51
输出:
C:ProjectsJavaPOCtest.csv
headers: [Year, Month, Company A, Company B, Company C, Company D, Company N]
data: [1990, Jan, 10, 15, 20, 31, 50]
data: [1990, Feb, 11, 14, 21, 30, 51]
Company B highest price 15.0 is Jan 1990
Company C highest price 21.0 is Feb 1990
Company N highest price 51.0 is Feb 1990
Company A highest price 11.0 is Feb 1990
Company D highest price 31.0 is Jan 1990
您应该将每一行都读作字符串。 然后,对于标题后的每一行,您可以遵循以下几种策略之一:为每个公司的股票价格创建一个日期数组和一个浮点数组
或者创建一个公司对象,该对象本身具有日期和股票价格数组)
您将需要在公司对象中使用"addDatePrice(date,price)方法。 您可以从标题 csv 行中的信息创建正确数量的公司(并为公司对象提供一个 nam)