综合实战_数据表转换（省份-城市）

省份--城市
1、要求可以通过一个城市找找到它所对应的省份信息；
2、可以通过一个省份找到所有城市的信息
第一步：先写基本字段

class Province {
    private int pid;
    private String pname;
    //setter, getter 和 无参构造省略
    public Province(int pid , String pname) {
        this.pid = pid;
        this.pname = pname;
    }
    public void getInfo() {
        return "省份编号：" + this.pid + "， 省份名称：" + this.pname;
    }
}

class City {
    private int cid;
    private String cname;
    //setter, getter 和 无参构造省略
    public City(int cid , String cname) {
        this.cid = cid;
        this.cname = cname;
    }
    public void getInfo() {
        return "城市编号：" + this.cid + "， 城市名称：" + this.cname;
    }
}

第二步：设置关键字段(引用)

class Province {
    private int pid;
    private String pname;
    private City[] cities;
    //setter, getter 和 无参构造省略
    public Province(int pid , String pname) {
        this.pid = pid;
        this.pname = pname;
    }
    public void setCity(City[] cities){
        this.cities = cities;
    }
    public City[] getCity() {
        return this.cities;
    }
    public void getInfo() {
        return "省份编号：" + this.pid + "， 省份名称：" + this.pname;
    }
}

class City {
    private int cid;
    private String cname;
    private Province province;
    //setter, getter 和 无参构造省略
    public City(int cid , String cname) {
        this.cid = cid;
        this.cname = cname;
    }
    public void setProvince(Province province) {
        this.province = province;
    }
    public Province getProvince() {
        return this.province;
    }
    public void getInfo() {
        return "城市编号：" + this.cid + "， 城市名称：" + this.cname;
    }
}

第三步：代码数据测试

public class Province_City {
    public static void main(String[] args) {
        //第一步：设置数据
        //1. 先准备好各自独立的对象
        Province p = new Province(1 , "江苏");
        City c1 = new City(2001 , "南京");
        City c2 = new City(2002 , "南通");
        City c3 = new City(2003 , "无锡");
        //2. 设置关系
        c1.setProvince(p);  //一个城市属于一个省份
        c2.setProvince(p);
        c3.setProvince(p);
        p.setCities(new City[]{c1 , c2 , c3});  //一个省份有多个城市
        //第二步：取出数据
        System.out.println(c1.getProvince().getInfo());
        for (int x=0; x < p.getCities().length ; x++) {
            System.out.println("\t|- " + p.getCities()[x].getInfo());
        }
    }
}