如何使用 Java 从文本文件中查找、读取和显示一行

Question

我有一个包含假飞机记录的文本文件。 我需要编写一个代码，该代码将根据其 ID 字符串查找记录并显示它。 我有一个主要的 class 和文本文件。 基本上用户应该能够输入“ID”，比如“DA0”，代码会找到它，并显示该行。

 /*
 * 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 文件

/*
 * 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;
    }
    
    
}

文本文件

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

case 2再次向用户询问 ID 并使用 Scanner 读取。

创建一个方法，在其中循环遍历您的airplaneSeats数组，如果输入的 ID 与数组中的一个AirplaneSeatRecords的 ID 匹配，则打印记录并中断循环。 您已经在AirplaneSeatRecords class 中有必要的方法。

另外，不要忘记在 switch 语句中添加默认情况。