package Mapping_transformation;

class item

{

    private long id ;

    private  String title ;

    private subitem subitems[] ;          //一个分类有多个子分类

    public item(long id , String title)

    {

        this.id = id ;

        this.title = title ;

    }

    public void setSubitems(subitem[] subitems) {

        this.subitems = subitems;

    }

    public subitem[] getSubitems() {

        return subitems;

    }

    public String getInfo()

    {

        return "【分类信息】id = "+this.id + " title = "+this.title ;

    }

}

class subitem

{

    private long id ;

    private  String title ;

    private item item ;

    public subitem(long id , String title)

    {

        this.id = id ;

        this.title = title ;

    }

    public void setItem(item item)

    {

        this.item = item ;

    }

    public item getItem()

    {

        return item ;

    }

    public String getInfo()

    {

        return "【子分类信息】id = "+this.id + " title = "+this.title ;

    }

}

public class One_to_many {

    public static void main(String[] args) {

        item item = new item(001,"编程书籍");

        subitem subitems[] = new subitem[]{

                new subitem(002,"java从入门到放弃"),

                new subitem(003,"c++从入门到放弃")

        };

        item.setSubitems(subitems);             //一个分类有多个子分类

        for(int i = 0 ; i<subitems.length ; i++)

        {

            subitems[i].setItem(item);

        }

        System.out.println(item.getInfo());

        for(int  i = 0 ; i<item.getSubitems().length ; i++)

        {

            System.out.println(item.getSubitems()[i].getInfo());

        }

    }

}

resul：
【分类信息】id = 1 title = 编程书籍

【子分类信息】id = 2 title = java从入门到放弃

【子分类信息】id = 3 title = c++从入门到放弃