Question

我正在尝试创建一个类，我可以在二进制搜索的帮助下快速将对象插入到类列表中。

这是我的班级和内部班级：

public class PostingsList implements Iterator<PostingsEntry>{

    /** The postings list */
    private ArrayList<PostingsEntry> list = new ArrayList<PostingsEntry>();

    class PostingsEntryComparator implements Comparator{
        @Override
        public int compare(PostingsEntry pA, PostingsEntry pB){
            if(pA.docID < pB.docID){
                return -1; 
            }   
            else if(pA.docID == pB.docID){
                return 0;
            }   
            else{
                return 1;
            }   
        }   
    }     

    public void add(PostingsEntry newPostingsEntry){ 
        //put in the right place
        PostingsEntryComparator pc = new PostingsEntryComparator();
        int res = Collections.binarySearch(list, newPostingsEntry, pc);
        if(res < 0){
            list.add(-res-1, newPostingsEntry);
        }
        else{
            System.out.println("already exists");
        }
    }
}

内部类用于比较list的对象，以便Collections.binarySearch可以工作。但是，我收到了这个错误。它是什么意思，我该怎么办呢？

n180-p69:new sahandzarrinkoub$ sh compile_all.sh
ir/PostingsList.java:22: error: PostingsList.PostingsEntryComparator is not abstract and does not override abstract method compare(Object,Object) in Comparator
    class PostingsEntryComparator implements Comparator{
    ^
ir/PostingsList.java:23: error: method does not override or implement a method from a supertype
        @Override
        ^

2 errors

Answer 1

class PostingsEntryComparator implements Comparator {
    ...
}

实施＆＃34; raw＆＃34; Comparator接口，接受Object个参数，即compare(Object,Object)。但是，这不是您要覆盖的内容，因为您的比较器特定于PostingsEntry。

因此，您需要实施Comparator<PostingsEntry>：

class PostingsEntryComparator implements Comparator<PostingsEntry> {
    ...
}

使用我自己的比较器尝试binarySearch时出错

1 个答案: