Java中利用循环计算城市间距离的教程

public class Cities {
    int cityID;
    float City_X_Location;
    float City_Y_Location;

    public void Initialization(int id, float x, float y) {
        this.cityID = id;
        this.City_X_Location = x;
        this.City_Y_Location = y;
    }

    public void Distance(float x, float y) {
        // 使用当前城市的坐标与传入的 (x, y) 计算距离
        int dist = (int) Math.sqrt(Math.pow(this.City_X_Location - x, 2) + Math.pow(this.City_Y_Location - y, 2));
        System.out.println(dist);
    }

    // 为了后续的equals方法，可能需要一个getter
    public int getCityID() {
        return cityID;
    }
    // 更好的实践是提供getter for X, Y coordinates
    public float getCity_X_Location() {
        return City_X_Location;
    }

    public float getCity_Y_Location() {
        return City_Y_Location;
    }

    // 重写equals方法以实现基于cityID的比较
    @Override
    public boolean equals(Object obj) {
        if (this == obj) return true;
        if (obj == null || getClass() != obj.getClass()) return false;
        Cities cities = (Cities) obj;
        return cityID == cities.cityID;
    }

    @Override
    public int hashCode() {
        return java.util.Objects.hash(cityID);
    }
}

public class Lab2 {
    public static Cities[] City = new Cities[4]; // 假设有4个城市

    public static void main(String[] args) {
        for (int i = 0; i < City.length; i++)
            City[i] = new Cities();

        City[0].Initialization(0, 1, 1);
        City[1].Initialization(1, 5, 5);
        City[2].Initialization(2, 10, 3);
        City[3].Initialization(3, 2, 7);

        // 手动计算示例：从City[0]到其他城市的距离
        // City[0].Distance(City[1].City_X_Location, City[1].City_Y_Location); // 3
        // City[0].Distance(City[2].City_X_Location, City[2].City_Y_Location); // 8
        // City[0].Distance(City[3].City_X_Location, City[3].City_Y_Location); // 6
        // ...以此类推，对于所有城市对进行手动编码，效率低下且易错
    }
}

// 错误的尝试
for (int i = 0; i < City.length; i++) {
    City[i].Distance(5, 5); // 错误：这里的5,5是硬编码，并非来自其他城市
    i++; // 错误：手动递增i会跳过一些城市，且无法正确配对
    City[i].Distance(10, 3);
    i++;
    City[i].Distance(2, 7);
    i++;
}

public class Lab2 {
    // ... (City数组和Initialization部分与上面相同) ...

    public static void main(String[] args) {
        // ... (初始化城市数据) ...

        System.out.println("--- 使用增强型for循环计算所有城市对距离 ---");
        // 外层循环：选择当前城市
        for (Cities currentCity : City) {
            // 内层循环：选择目标城市
            for (Cities otherCity : City) {
                // 避免城市与自身进行比较
                if (!currentCity.equals(otherCity)) { // 假设Cities类已正确重写equals方法
                    // 调用当前城市的Distance方法，传入目标城市的坐标
                    System.out.print("距离从 City[" + currentCity.getCityID() + "] 到 City[" + otherCity.getCityID() + "]: ");
                    currentCity.Distance(otherCity.getCity_X_Location(), otherCity.getCity_Y_Location());
                }
            }
        }
    }
}

public class Lab2 {
    // ... (City数组和Initialization部分与上面相同) ...

    public static void main(String[] args) {
        // ... (初始化城市数据) ...

        System.out.println("--- 使用传统索引型for循环计算所有城市对距离 ---");
        // 外层循环：选择当前城市的索引
        for (int i = 0; i < City.length; i++) {
            // 内层循环：选择目标城市的索引
            for (int j = 0; j < City.length; j++) {
                // 避免城市与自身进行比较
                if (i != j) { // 比较索引即可避免自身比较
                    // 获取当前城市和目标城市对象
                    Cities currentCity = City[i];
                    Cities otherCity = City[j];

                    // 调用Distance方法
                    System.out.print("距离从 City[" + currentCity.getCityID() + "] 到 City[" + otherCity.getCityID() + "]: ");
                    currentCity.Distance(otherCity.getCity_X_Location(), otherCity.getCity_Y_Location());
                }
            }
        }
    }
}