Question

我有一个班级：

public class FootballPlayer() {

    private int scoredGoals;
    //... some other attributes and some getters and setters
}

我需要在我的drools文件中有一个规则来决定谁是两个comapred玩家之间更好的玩家。

我遇到的困难是如何比较同一类的两个对象？

非常感谢你！

Answer 1

没有困难，只有一个小小的悬崖必须环游。

rule "A better scorer"
when
    $f1: FootballPlayer( $score1; scoredGoals )
    $f2: FootballPlayer( $score2; scoredGoals > $score1 )
then
    System.out.println( $f2.getName() + " is better than " + $f1.getName() );
end

当然，两位球员可能并列：

rule "Two scorers with equal cpability"
when
    $f1: FootballPlayer( $score1; scoredGoals )
    $f2: FootballPlayer( this != $f1, $score2; scoredGoals == $score1 )
then
    System.out.println( $f2.getName() + " and " + $f1.getName() + " are in the same class" );
end

注意确保第二个与第一个不相符的约束！（这是“悬崖”。）

您可能还对确定最佳状态的规则感兴趣：

rule "The best scorer"
when
    $f1: FootballPlayer( $score1; scoredGoals )
    not FootballPlayer( scoredGoals > $score1 )
then
    System.out.println( $$f1.getName() + " is the best" );
end

Answer 2

我建议的解决方案是实现类似的界面;那样你将能够根据得分目标对球员名单进行排序。

public class FootballPlayer implements Comparable<FootballPlayer>
{
    private int scoredGoals;

    public FootballPlayer(int scoredGoals)
    {
        this.scoredGoals = scoredGoals;
    }

    public static void main(String... args)
    {
        FootballPlayer a = new FootballPlayer(10);
        FootballPlayer b = new FootballPlayer(5);
        FootballPlayer c = new FootballPlayer(15);
        List<FootballPlayer> fps = new ArrayList<FootballPlayer>();
        fps.add(a);
        fps.add(b);
        fps.add(c);
        Collections.sort(fps);
        for (FootballPlayer fp : fps)
        {
            System.out.println(fp);
        }
    }

    @Override
    public String toString()
    {
        return " -- " + scoredGoals;
    }

    @Override
    public int compareTo(FootballPlayer o)
    {
        if (o == null)
        {
            return 1;
        }
        if (o.scoredGoals < this.scoredGoals)
        {
            return -1;
        }
        else if (o.scoredGoals > this.scoredGoals)
        {
            return 1;
        }
        else
        {
            return 0;
        }
    }
}

规则语言：如何处理同一类的2个对象之间的比较？

2 个答案: