java - 通过 Arraylist 进行查询

Question

我正在构建一个程序来读取 .txt归档并提取学生数据并将其存储在集合中。然后用户应该能够选择几个不同的查询。我请求帮助的查询是选择所有毕业的学生(例如 2014 年毕业的学生)，然后将这些结果打印到屏幕上。

简而言之，我如何搜索抛出 Arraylist存储在 ProcessRecords例如，为 2014 年毕业的学生开设的类(class)？由于某种原因，我似乎无法返回特定年份毕业的学生的记录。

下面是我的代码。

第一类:ProcessRecords(带有 main 方法)

import java.util.*;
import java.io.*;

 public class ProcessRecords {

public static void AskUser()
throws Exception {
    Scanner preference = new Scanner(System.in);
    //Creating a new scanner will allow us to gather user input

    boolean flag=true; 
    //I will use this for my while loop
    while (flag) {
        System.out.println("What type of Search would you like to run?\n 1)Search for all students\n 2) Search for students graduating in a specific year\n 3)Search for students whose last name begins with a certain string\n");
        int searchType=preference.nextInt();
        //This variable will store what type of query the user would like to run

        switch(searchType) {
            case 1:
            System.out.println("Gathering Records for all students\n");
            //Call Query Method in the Query Class to return all students in the collection
            break;
            //Call Query Method in the Query Class to return all students in the colletion
            case 2: System.out.println("What graduation year would you like to search for? \n"); 
            String yearsearch=preference.next(); 
            query.getYear(Integer.parseInt(yearsearch));
            //getYear();
            break;
            //Call Query Method to return students who are graduating in the specified year
            //Pass the "yearsearch" variable to the Query class
            case 3:
            System.out.println("What string would you like to search for? \n");
            String lstsearch=preference.next();
            break;
            default:
            System.out.println("Please pick a number between 1 and 3") ;
            break;
            //Call Query Method in the Query Class to return students who have the string in their last name
            //Also I need to pass the "lstsearch" variable to the Query class to search through last names                

        }
    }
}

public static void main(String[] args)
throws Exception
{
    Scanner input = new Scanner(new File("students.txt"));
    //This will import the file
    input.nextLine();
    //This will skip the headers in the file
    System.out.println("Processing file now...");
    //Let the user know that the file is being processed

    int id;
    String last;
    String first;
    int year;
    int i=1;
    // Declare variables that we will extract from the file

    //Now we will being processing the file with a while loop

    List<StudentRecord> studentRecords = new ArrayList<StudentRecord>();
    while(input.hasNext())
    {
        id=input.nextInt();
        last=input.next();
        first=input.next();
        year=input.nextInt();
        StudentRecord record = new StudentRecord(id, last, first, year);
        studentRecords.add(record);
        System.out.println(id + "  " + last + "  " + first + "  " + year + "\n");

    }
    System.out.println(" You have successfully read and printed from the file!");
    for (StudentRecord s : studentRecords)
        System.out.println(s.toString());

    Query query = new Query(studentRecords);
  }
}

第二类:StudentRecord

import java.util.*;
public class StudentRecord
{
private int id;
private String last;
private String first;
private int year;

public StudentRecord(int id, String last, String first, int year)
{
    this.id=id;
    this.last=last;
    this.first=first;
    this.year=year;
}

public String toString()
{
    return id + "  " + last + "  " + first + "  " + year;
} 

public int getYear()
{

    return year;
}

第三类:查询

import java.util.*;
import java.io.*;

public class Query
{
private List<StudentRecord> records;

public Query(List<StudentRecord> records) {
    this.records = records;
}

public void getYear(int yearSearch) {
    //I am trying to create a method to get students who are graduating in a specific year.
    // I want to call this method in the ProcessRecord SwitchCase Case #2
    int count = 0;

    for(StudentRecord record : records) {
        if(record.getYear() == yearSearch) {
           System.out.println(record.toString());
            count++;
        }
    }


}
}

问题

如果你能帮我弄清楚如何搜索 Arraylist包含特定年份毕业的学生的学生记录，然后将整行打印到屏幕上，那就太棒了!我对编程非常陌生，因此我感谢您为我提供的所有帮助。

Answer 1

public void getYear(int yearSearch) {
//I am trying to create a method to get students who are graduating in a specific year.
// I want to call this method in the ProcessRecord SwitchCase Case #2
int count = 0;

for(StudentRecord record : records) {
    if(record.getYear() == yearSearch) {
       System.out.println(record.getId()+" " + record.getFirst()+ " "+ record.getLast() + "+record.getYear());
        count++;
    }
}
}