Question

我正在尝试比较用户在ProcessRecords类中的案例3中输入的字符串。我然后尝试将该字符串与Arraylist中的每个姓氏进行比较，如果记录与用户的输入匹配，那么我想打印它。我不知道如何做到这一点但我会感谢任何指导。

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(4) Exit\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");
            //Query.getAll();
            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"); 
            int yearsearch=preference.nextInt(); 

            Query.getYears(yearsearch);
            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();
            Query.getLast(lstsearch);
            break;

            case 4:
            System.out.println("You have chosen to exit the program. Thank you!");
            flag=false;
            break;

            default:
            System.out.println("Please pick a number between 1 and 4") ;
            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 List<StudentRecord> studentRecords;
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);
 }
}

+++++++++++++++++++++++++++++++++++ 下一课

 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;
}

public String getLast()
{
    return last;
  } 

   }

+++++++++++++++++++++++++++++++++++ 下一课

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

public class Query
{
static List<StudentRecord> records;
public List<StudentRecord> studentRecords;

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

public static void getYears(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;

    System.out.println("ID" +"  " +"Last" + "  " + "First" + "  " + "Year \n");
    for(StudentRecord record : records) {
        if(record.getYear() == yearSearch) {
            System.out.println((record.toString()));
            count++;
        }
        System.out.printf("\n");
    }

}

public static void getLast(String lstsearch){

    int count =0;
    System.out.println("ID" +"    " +"Last" + "    " + "First" + "    " + "Year \n");
    int sizes= lstsearch.length();
    System.out.println(lstsearch);

    for(StudentRecord record : records) {
        System.out.println(count);
        if(record.getLast() == lstsearch) {
            System.out.println((record.toString()));
            count++;
        }
    }
}
public void getAll(){
 for (StudentRecord s : studentRecords)
        System.out.println(s.toString());
 }

}

再次，我正在寻找搜索arraylist的帮助，如果数组列表中的姓氏以字符串开头，即“g”，那么我想打印它。谢谢你的帮助！

Answer 1

public static StudentRecord searchRecords(Collection<StudentRecord> records, String lastName)
{
    for (StudentRecord record : records)
    {
        if (lastName.equalsIgnoreCase(record.getLast()))
            return record;
    }
    return null;
}

这将在您的数组中搜索相应的记录。如果存在则返回该记录 - 否则返回null。如果您将来有这样的问题，可以随时咨询appropriate javadoc，了解可用于比较对象的一些方法。

将Arraylist与String进行比较

1 个答案: