如何修復此編程代碼？ （MOOCFI java week7 練習8）

Question

我正在關注 Moocfi 練習 8（Java 在線課程），但我無法調試我的編程代碼。 https://materiaalit.github.io/2013-oo-programming/part2/week-7/ （我問的問題在頁面最底部，名為“機場”）

機場.java

import java.util.Scanner;
import java.util.HashMap;
import java.util.ArrayList;

public class Airport { 

    private HashMap<Plane, Flight> num;
    private Scanner read;
    private ArrayList<Plane> planes;

    public Airport(){
    read = new Scanner(System.in);
    this.num = new HashMap<Plane, Flight>();
    planes = new ArrayList<Plane>();

    }


    public void start(){

        while(true){
        System.out.print("Choose operation:\n[1] Add airplane" + "\n[2] Add flight\n[x] Exit\n> ");
        String ans = read.nextLine();
        if (ans.equals("1")){
            num1();

        } else if (ans.equals("2")){
            num2();

        } else if (ans.equals("x")){
            break;
        } else continue;
        }

        System.out.println("\nFlight service\n------------\n");

        while(true){

        System.out.print("Choose operation:\n[1] Print planes\n"
                + "[2] Print flights\n[3] Print plane info\n[x] Quit\n> ");
        String ans2 = read.nextLine();
        if (ans2.equals("1")){
            nus1();

        }
        else if (ans2.equals("2")){
            nus2();

        }
        else if (ans2.equals("3")){
            nus3();

        } 
        else if (ans2.equals("x")){
            break;
        }
        else continue;
        }
    }

    public void num1(){
        System.out.print("Give plane ID: ");
        String pi = read.nextLine();
        System.out.print("Give plane capacity: ");
        int pin = read.nextInt();
        planes.add(new Plane(pi, pin));
        System.out.println("");
    }

    public void num2(){
        System.out.print("Give plane ID: ");
        String pi = read.nextLine();
        System.out.print("Give departure airport code: ");
        String pin = read.nextLine();
        System.out.print("Give destination airport code: ");
        String pim = read.nextLine();
        for (Plane a:planes){
            if (a.getName()==pi){
                Plane b = new Plane(a.getName(), a.getCap());
                num.put(b, new Flight(pin, pim));
            }
        }
        System.out.println("");
    }

    public void nus1(){
        for (Plane p: planes){
            System.out.println(p.getName() + " (" + p.getCap() + " ppl)");            
        }
        System.out.println("");
    }

    public void nus2(){
        for (Plane p : num.keySet()){
            System.out.println(p.getName() + " (" + 
                    p.getCap() + " ppl) " + num.get(p));
        }
        System.out.println("");
    }

    public void nus3(){
        System.out.print("Give plane ID: ");
        String b = read.nextLine();
        for (Plane a: planes){
            if (a.getName().equals(b)){
                System.out.println(a.getName() + " (" + a.getCap() + " ppl)");
            }
            System.out.println("");
        }
    }


}

飛機.java

public class Plane {
    private String name;
    private int capacity;

    public Plane(String name, int capacity){
        this.name = name;
        this.capacity = capacity;
    }

    public String getName(){
       return name;
    }

    public int getCap(){
       return capacity;
    }
}

飛行.java

public class Flight {
    private String departureCode;
    private String destinationCode;

    public Flight(String departureCode, String destinationCode){
        this.departureCode = departureCode;
        this.destinationCode = destinationCode;
    }

    public String toString(){
        return "(" + departureCode + "-" + destinationCode + ")";
    }
}

主程序

public class Main {
    public static void main(String[] args) {
        Airport a = new Airport();
        a.start();
        // Write your main program here. Implementing your own classes will be useful.
    }
}

我想弄清楚兩個問題：

1. 當我運行程序並按 1 並保存飛機信息時，它會打印出以下語句兩次，這應該只是一次。

System.out.print("Choose operation:\n[1] Add airplane" + "\n[2] Add flight\n[x] Exit\n> ");

2. 另外，在 Airport.java 上，我將航班信息保存在一個 HashMap 變量中以便稍后打印出來，但是當我運行程序時它似乎不起作用。

Answer 1

這是nextInt()的問題，當您按 Enter 時它不會考慮換行符。 使用nextLine()並將其轉換為 int

在num1()方法中，替換

int pin = read.nextInt();

和

int pin = Integer.parseInt(read.nextLine());

談到您的HashMap問題，您正在使用==比較字符串。 使用equals

在num2()方法中，替換

if (a.getName() == pi)

和

if (a.getName().equals(pi))