java - 没有警告的通用接口(interface)比较器

Question

给定:

public interface PrimaryKey<Key extends Comparable> {
    Key getKey();
}

和

public class PrimaryKeyComparator implements Comparator<PrimaryKey> {
    public int compare(PrimaryKey first, PrimaryKey second) {
        return first.getKey().compareTo(second.getKey());
    }
}

此组合有效，但会给出有关原始类型的警告。我尝试了多种添加类型参数的方法，但我尝试过的每一种组合都会破坏代码。

Answer 1

试试这个:

public interface PrimaryKey<TKey extends Comparable<TKey>> {
    TKey getId();
}

public class PrimaryKeyComparator<TKey extends Comparable<TKey>> 
                                 implements Comparator<PrimaryKey<TKey>> {
    public int compare(PrimaryKey<TKey> first, PrimaryKey<TKey> second) {
        return first.getId().compareTo(second.getId());
    }
}