java - 在 objectdb 中查询

Question

我必须在 objectdb 中实现一个查询并且几乎没有什么想法。

问题是写一个查询

Returns the collection of all laptops each of which has at least one
          other laptop preinstalled with the same processor.

我的笔记本电脑课是

public class Laptop {

    String modelName; // key
    int price;        // in dollars
    boolean hasHDScreen; // has a HD Screen ?
    int hardDriveCapacity; // in GB

    Processor processor;  // the preinstalled processor
    Memory memory; // the preinstalled memory
    Company madeBy; // the inverse of company.makeLaptops
}

我的处理器类是

public class Processor {

    String modelName; // key 
    float clockSpeed; // in gigahertz (GHz)

    Company madeBy; // the inverse of Company.makeProcessors
}   

我的函数定义也如下所示

public static Collection<Laptop> sameProcessor(Query q) {
        /* Returns the collection of all laptops each of which has at least one
         * other laptop preinstalled with the same processor.
         */
        q.setClass(Laptop.class);
        q.setFilter("this.processor == ");

    } 

我怎样才能实现它？SQL 也可以。

谢谢

Answer 1

终于熬过了这一关。这是解决方案

public static Collection<Laptop> sameProcessor(Query q) {
        /* Returns the collection of all laptops each of which has at least one
         * other laptop preinstalled with the same processor.
         */

        Collection result = new HashSet<Laptop>();
        q.setClass(Laptop.class);

        Collection allLaptops = (Collection) q.execute();

        Iterator it = allLaptops.iterator();

        while(it.hasNext()) {
            Laptop currentLaptop = ((Laptop)it.next());
            Processor p = currentLaptop.processor;
            if(p.installedOn(q).size()>=2) {

                result.add(currentLaptop);
            }
        }

        return (Collection<Laptop>)result;       
    } 

使用的方法installedOn定义如下：

public Collection<Laptop> installedOn(Query q) {

     /* Returns the collection of all laptops on which the target memory 
        is preinstalled. Represents the inverse of Laptop.memory.
     */
        Memory memory = this;
        q.setClass(Laptop.class);
        q.declareParameters("Memory m");
        q.setFilter("this.memory == m");
        Collection result = (Collection)q.execute(memory);
        return (Collection<Laptop>) result;

    }

谢谢。希望能帮助到你。