[英]Java Data Type for CSV File processing
我正在解決這個問題,找到一個合適的數據類型,但我不能解決哪一個是最有效和簡單的方法來編程,而不使用任何第三方庫:
問題:考慮CSV文件中自1990年以來每月給出的N個公司的股價。 文件格式如下,第一行為標題。
Year,Month,Company A, Company B,Company C, .............Company N
1990, Jan, 10, 15, 20, , ..........,50
1990, Feb, 10, 15, 20, , ..........,50
.
.
.
。 2013年9月,50日,10日,15日............ 500
輸出:股票價格最高的每個公司年月的清單。
我考慮過使用樹木,Hashmap,列表,但我無法完成THE ONE解決方案。 到目前為止,我是Java的新手,有幾周的Java編碼經驗。 任何形式的偽代碼,程序或使用什么數據類型的幫助都是值得贊賞的。
好的,有無數種方法可以做到這一點,但我最喜歡的方法是創建一個Company類來持有Company.name,Company.month,Company.year,Company.price並使用Map添加數據。 然后,添加邏輯將檢查地圖以查看是否存在具有相同名稱的公司,如果不存在或新公司價格較大,則只需將新公司數據放入具有公司名稱作為關鍵字的地圖中。 好吧,下面的代碼只是為了演示目的,我會使用eclipse生成getters / setter並使用那些代替直接成員變量,就像演示一樣。 此演示缺少從CSV文件中讀取和收集公司數據。
CompanyLoader.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();
}
}
Company.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 + "]";
}
}
test.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
輸出:
C:\Projects\Java\POC\test.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
好 。 你應該把每一行都讀成一個字符串。 然后,對於標題之后的每一行,您可以遵循以下幾種策略之一:創建日期數組,以及每個公司股票價格的浮點數組
或者創建一個公司對象,其本身具有日期和股票價格的數組)
您將需要在Company對象中使用“addDatePrice(date,price)方法。您可以在標題csv行中創建正確數量的公司(並將公司對象賦予nam)
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