如何打印出hashmap商店

Question

import java.util.Scanner;


public class MainApp 
{
    private Scanner keyboard = new Scanner(System.in);
    public static void main(String[] args)
    {
        new MainApp().start();  
    }

    public void start()
    {
        Airline airline1 = new Airline("AerLingus");
        PlaneStore planeStore = new PlaneStore("Aer Lingus");

        Flight p1 = new Flight("Aer Lingus","A01", 150.5, 10.5, 500, Flight.AIRPLANETYPE.AIRBUS);
        Flight p2 = new Flight("Aer Lingus","B01", 50.3, 1.5, 91, Flight.AIRPLANETYPE.CORPORATE);
        Flight p3 = new Flight("Aer Lingus","C01", 12.2, -3.1, 56, Flight.AIRPLANETYPE.AIRBUS);


        Flight p4 = new Flight("Ryan Air","D01", 10.5, 1.5, 430, Flight.AIRPLANETYPE.PRIVATE);
        Flight p5 = new Flight("Ryan Air","E01", 0.3, 2.1, 101, Flight.AIRPLANETYPE.CORPORATE);
        Flight p6 = new Flight("Ryan Air","F01", 2.2, -3, 291, Flight.AIRPLANETYPE.AIRBUS);
        planeStore.add(p1);
        planeStore.add(p2);
        planeStore.add(p3);
        planeStore.print();

        airline1.add(planeStore);
        airline1.add(planeStore);
        airline1.add(planeStore);

        airline1.printPlane();
    }

}

import java.util.HashMap;


public class Airline 
{
    private String airlineName;
    private HashMap<String, PlaneStore> map;

    public Airline(String airlineName)
    {
        this.airlineName = "";
        map = new HashMap<String, PlaneStore>();
    }
    public void add(PlaneStore plane)
    {
        map.put(airlineName, plane);
    }
    public void remove(String flight)
    {
        map.remove(flight);
    }
    public void printPlane()
    {
        System.out.println("\n********Flight List********");
        for (PlaneStore plane: map.values()) {
             //System.out.println(plane);
            // class
            // or:
            System.out.println(airlineName);
            System.out.println(plane.toString());

        }

    }

}

嘿，我想打印出飞机存储。飞机存储包含字符串和航班的哈希图。这就是flight.add/print进入主端的地方。但我现在希望航空公司和航班并行打印，所以我把航空公司商店和我试图打印出PlaneStore以及航空公司，但我得到的只是一个内存地址，有人能帮我吗？

Answer 1

因为你似乎是编程新手，我要给你答案：

public class PlaneStore {

    private String name;
    ...

    public String toString() {
        return name;
    }
}

Answer 2

您可以通过以下方式实现：

System.out.println(map.toString());

这与

System.out.println(map);

然后，为了避免您提到的“内存地址”：

public String toString() {
    return this.storeName; // or similar, 
}

这之所以有效，是因为Map可以通过调用每个键和值的toString（）方法来打印其内容。

如果这个输出不够好，您必须自己迭代：使用map.entrySet（）并迭代它。

Answer 3

如果您得到类似于<代码>MyClass@abcdef，则需要在MyClass中重写字符串，如下所示：

public class MyClass {

    ...

    @Override
    public String toString() {
        return "My class"; // Make a string here that you want to display
    }
}

因此，例如，如果PlaneStore对字段具有int planeCount和字符串名称，则可以执行如下操作：

@Override
public String toString() {
    return "Plane store | Name: " + name + ", planes: " + planeCount;
}