如何使用 Java 从文本文件中查找、读取和显示一行

Question

I have a text file entailing fake airplane records. I need to write a code that will find a record based on its ID String and display it. I have a main, class, and text file. Basically the user should be able to enter the "ID" say 'DA0' and the code will find it, and display the line.

 /*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package lastassignment;

import java.io.FileInputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Scanner;

/**
 *
 * @author djiml
 */
public class LastAssignment {
    
    public LastAssignment() {
        
    }
    
    private ArrayList<AirplaneSeatRecords> airplaneSeats = new ArrayList<AirplaneSeatRecords>();
        Scanner scnr = new Scanner(System.in);
        String airlineIndex;
        String name;
        int seat;
        double ticketCost;

    public void OpenRecord() throws IOException {
        FileInputStream inputfile = new FileInputStream("input.txt");
        Scanner inFile = new Scanner(inputfile);
        
        while (inFile.hasNext()) {
            airlineIndex = inFile.next();
            ticketCost = inFile.nextDouble();
            seat = inFile.nextInt();
            name = inFile.nextLine();
            airplaneSeats.add(new AirplaneSeatRecords(airlineIndex, ticketCost, seat, name));
        }
        inFile.close();
    }
    
    public static void main(String[] args) throws IOException {
        Scanner scnr = new Scanner(System.in);
        int input;
        
        
        System.out.println("What would you like to do?:");
        System.out.println("1. Open a Record.");
        System.out.println("2. Display a Record.");
        System.out.println("3. Display All Records.");
        System.out.println("4. Add a New Record.");
        System.out.println("5. Edit a Record.");
        System.out.println("6. Delete a Record.");
        System.out.println("7. Save Progress.");
        System.out.println("8. Exit.");
        System.out.print(": ");
        
        input = scnr.nextInt();
        
        if (input != 8) {
            
            switch(input) {
            
            case 1 ->  new LastAssignment().OpenRecord();
            
            case 2 -> System.out.println("FIXME: Add 'Display a Record'");
            
            case 3 -> System.out.println("FIXME: Add 'Display All Records'");
            
            case 4 -> System.out.println("FIXME: Add 'Add a New Record'");
            
            case 5 -> System.out.println("FIXME: Add 'Edit a Record'");
            
            case 6 -> System.out.println("FIXME: Add 'Delete a Record'");
            
            case 7 -> System.out.println("FIXME: Add 'Save Progress'");
        
        }
            
        }
        else {
            System.out.println("FIXME: Add 'Exit'");
        }
    }
    
}

Class File

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package lastassignment;

/**
 *
 * @author djiml
 */
public class AirplaneSeatRecords {
    private String airlineIndex;
    private double ticketCost;
    private String customerFlying;
    private int seatNum;
    
    public AirplaneSeatRecords() {
        // Constructor
    }
    
    public AirplaneSeatRecords(String ID, double cost, int seat, String name) {
        airlineIndex = ID;
        ticketCost = cost;
        seatNum = seat;
        customerFlying = name;
    }
    
    public void displayTickets() {
        System.out.printf("%8s \t %-20s \t\t $%.2f \t %d \n", airlineIndex, customerFlying, ticketCost, seatNum);
    }
    
    public String getTicketID() {
        return airlineIndex;
    }
    
    public double getTicketCost() {
        return ticketCost;
    }
    
    public int getSeatNum() {
        return seatNum;
    }
    
    public String getCustomerName() {
        return customerFlying;
    }
    
    public void setSeatNum(int seat) {
        seatNum = seat;
    }
    
    public void setCustomerName(String name) {
        customerFlying = name;
    }
    
    public void setTicketPrice(double price) {
        ticketCost = price;
    }
    
    
}

Text File

DA0 215.00 19 Doug Anderson
DA1 200.00 20 Drew Bates
DA2 185.00 21 Theresa Patty
DA3 170.00 22 Andrew Abrams

Answer 1

In case 2 ask the user again for an ID and read it with Scanner.

Create a method where you iterate in a loop through your airplaneSeats array, and if the entered ID matches the ID of one of the AirplaneSeatRecords in your array, then print the record and break the loop. You already have the necessary methods for it in the AirplaneSeatRecords class.

Also, don't forget to add a default case to your switch statement.