使用对象和输入数据 JAVA 进行赋值

Question

所以我的任务是创建一个名为 city 的对象，并具有城市的经度、纬度和名称，然后询问城市的数量，然后用户将名称、经度和纬度输入到数组中以供访问。我将如何用我现在拥有的东西来实现这一点？

import java.util.Scanner;
public class Assignment3 {
public static void main(String[] args) {
Scanner lat = new Scanner(System.in);  //for double data
Scanner lon = new Scanner(System.in);  //for double data
Scanner city = new Scanner(System.in); //for string data
Scanner in = new Scanner(System.in);  //for int
System.out.print("How many cities? ");
int number = in.nextInt();

City [] cities = new City [number];
for(int i = 1; i <= number; i++){
System.out.println("City # " + i);
System.out.print("Enter name: " );
String name = city.Next();
System.out.print("Enter longitude: ");
double longitude = lon.nextDouble();
System.out.println("Enter latitude: ");
double latitude = lat.nextDouble();
}
}
}

public class City {
String name;      //name of cities
double lon, lat;  //longitude & latitude
City(String name, double lon, double lat) 
{
this.name = name;
this.lon = lon;
this.lat = lat;
}


public void report(){    //should report current position of a city
System.out.println("City: " + this.name); // displays city name
System.out.println("Longitude: " + this.lon);  //displays longitude
System.out.println("Latitude: " + this.lat);    //displays latitude
}
public double distanceFrom(City otherCity){  //should calculate the distance
return 0;
}
}

关键是这样您就可以询问城市的直接位置，然后询问它们之间的距离。任何帮助都非常感谢，谢谢

Answer 1

您可以通过以下简单方法实现这一点：

将类City的 setter 实例方法定义为您希望用户输入的每个属性，然后在主程序中迭代每个城市对象并设置其信息：

public static void main(String[] args) {
Scanner input = new Scanner(System.in); 
System.out.print("How many cities? ");
int number = input.nextInt();
City [] cities = new City [number];
for(int i = 0; i < number; i++){
cities[i] = new City(); // create new object of City
System.out.println("City # " + (i+1));
System.out.print("Enter name: " );
String name = input.next();
cities[i].setName(name);
System.out.print("Enter longitude: ");
double longitude = input.nextDouble();
cities[i].setLongitude(longitude);
System.out.print("Enter latitude: ");
double latitude = input.nextDouble();
cities[i].setLatitude(latitude);
}
}
public class City {
private String name;      //name of cities
private double lon, lat;  //longitude & latitude
City(){  // default constructor
name="";
this.lon = 0;
this.lat = 0;
}
City(String name, double lon, double lat) 
{
this.name = name;
this.lon = lon;
this.lat = lat;
} 
public void setName(String n){
name = n;
}
public void setLongitude(double longitude){
lon = longitude;
}
public void setLatitude(double latitude){
lat = latitude;
}
}  

Answer 2

不确定我是否理解您的问题，但您需要使用您在 for 循环中收集的当前信息创建一个城市对象。然后将其保存在您的城市数组中。

for(int i = 0; i < number; i++){
System.out.println("City # " + (i+1));
System.out.print("Enter name: " );
String name = city.Next();
System.out.print("Enter longitude: ");
double longitude = lon.nextDouble();
System.out.println("Enter latitude: ");
double latitude = lat.nextDouble();
City a_city = new City(name,longitude,latitude);
cities[i] = a_city;
}

我将你的 for 循环从 i=1 更改为 i=0

要找到两个城市之间的距离，您可能需要查看这篇文章 计算两个经纬度点之间的距离？(哈弗斯公式)