Java Collections.sort（）不比較元素

Question

我有一個IndexEntry的ArrayList，它是一個帶字符串的簡單類，以及兩個整數和一個compareTo()方法，如下所示。 我的問題是，當我在ArrayList上調用Collections.sort()時，大多數時候所有內容都正確排序，但有時兩個元素永遠不會被比較，從而導致列表排序錯誤。

一些代碼供參考：

//Get a list of the values
ArrayList<IndexEntry<T>> cleanEntries = new ArrayList<IndexEntry<T>>(matches.get(query).values());

//Sort Files/URLS
Collections.sort(cleanEntries);

public int compareTo(IndexEntry<T> other) {
    if(this.occurrenceCount < other.getOccurrenceCount()){
        return 1;
    }
    else if(this.occurrenceCount > other.getOccurrenceCount()){
        return -1;
    }
    else{//Need to compare Initial Positions
        if(this.firstOccurrence == other.getFirstOccurrence()){
            return this.getLocationName().compareTo(other.getLocationName());
        }
        else if(this.firstOccurrence > other.getFirstOccurrence()){
            return 1;
        }
        else{
            return -1;
        }
    }
}   

以下是所有IndexEntry的字母“C”的示例輸出：

c
"index.html", 6, 2
"chickadee.html", 3, 2
"cuckoo.html", 3, 2
"crow.html", 3, 2
"crane.html", 3, 2
"cardinal.html", 3, 2
"quail.html", 2, 2
"robin.html", 2, 2
"finch.html", 2, 2
"kingfisher.html", 2, 2
"swan.html", 2, 2
"turkey.html", 2, 2
"ibis.html", 2, 2
"falcon.html", 2, 2
"albatross.html", 2, 2
"tern.html", 2, 2
"dove.html", 2, 2
"mockingbird.html", 2, 2
"owl.html", 2, 2
"sparrow.html", 2, 2
"hawk.html", 2, 2
"magpie.html", 2, 2
"nighthawk.html", 2, 2
"gull.html", 2, 2
"bluebird.html", 2, 2
"raven.html", 2, 2
"blackbird.html", 2, 2
"sandpiper.html", 2, 2
"pheasant.html", 2, 2
"roadrunner.html", 2, 2
"duck.html", 2, 2
"vulture.html", 2, 2
"pigeon.html", 2, 2
"heron.html", 2, 2
"stork.html", 2, 2
"warbler.html", 2, 2
"woodpecker.html", 2, 2
"hummingbird.html", 2, 2
"mallard.html", 2, 2
"osprey.html", 2, 2
"swallow.html", 2, 2
"wren.html", 2, 2
"goose.html", 2, 2
"meadowlark.html", 2, 2
"pelican.html", 2, 2
"starling.html", 2, 2
"loon.html", 2, 2
"eagle.html", 2, 2
"puffin.html", 2, 2
"egret.html", 2, 2

注意在發生計數和初始發生之后如何確定它是否相同它停止排序。 正確的輸出將是：

c
"index.html", 6, 2
"cardinal.html", 3, 2
"chickadee.html", 3, 2
"crane.html", 3, 2
"crow.html", 3, 2
"cuckoo.html", 3, 2
"albatross.html", 2, 2
"blackbird.html", 2, 2
"bluebird.html", 2, 2
"dove.html", 2, 2
"duck.html", 2, 2
"eagle.html", 2, 2
"egret.html", 2, 2
"falcon.html", 2, 2
"finch.html", 2, 2
"goose.html", 2, 2
"gull.html", 2, 2
"hawk.html", 2, 2
"heron.html", 2, 2
"hummingbird.html", 2, 2
"ibis.html", 2, 2
"kingfisher.html", 2, 2
"loon.html", 2, 2
"magpie.html", 2, 2
"mallard.html", 2, 2
"meadowlark.html", 2, 2
"mockingbird.html", 2, 2
"nighthawk.html", 2, 2
"osprey.html", 2, 2
"owl.html", 2, 2
"pelican.html", 2, 2
"pheasant.html", 2, 2
"pigeon.html", 2, 2
"puffin.html", 2, 2
"quail.html", 2, 2
"raven.html", 2, 2
"roadrunner.html", 2, 2
"robin.html", 2, 2
"sandpiper.html", 2, 2
"sparrow.html", 2, 2
"starling.html", 2, 2
"stork.html", 2, 2
"swallow.html", 2, 2
"swan.html", 2, 2
"tern.html", 2, 2
"turkey.html", 2, 2
"vulture.html", 2, 2
"warbler.html", 2, 2
"woodpecker.html", 2, 2
"wren.html", 2, 2

無論如何，就像我說我必須省略很多信息，但如果有什么想到的話，我真的很感激想法。 事實上，在創建ArrayList之后，“匹配”數據結構不會被修改。

編輯：嘿，我還在讀你的回答。 非常感謝您的快速幫助！ 以下是整個IndexEntry類，因為你們中的一些人問：

    class IndexEntry<extends Comparable<T>> implements Comparable<IndexEntry<T>>{
        private T theLocation;
        private Integer occurrenceCount;
        private Integer firstOccurrence;

        public IndexEntry(T location, Integer firstOcc, Integer occCount){
            theLocation = location;
            occurrenceCount = occCount;
            firstOccurrence = firstOcc;
        }

        public int compareTo(IndexEntry<T> other) {         
            if(this.occurrenceCount < other.getOccurrenceCount()){
                return 1;
            }
            else if(this.occurrenceCount > other.getOccurrenceCount()){
                return -1;
            }
            else{//Need to compare Initial Positions
                if(this.firstOccurrence == other.getFirstOccurrence()){
                    return this.getLocationName().compareTo(other.getLocationName());
                }
                else if(this.firstOccurrence > other.getFirstOccurrence()){
                    return 1;
                }
                else{
                    return -1;
                }
            }
        }   

        public String getLocationName(){
            if(theLocation instanceof File){
                return ((File) theLocation).getAbsolutePath();
            }
            else{
                return theLocation.toString();
            }
        }

        public Integer getFirstOccurrence(){
            return firstOccurrence;
        }

        public Integer getOccurrenceCount(){
            return this.occurrenceCount;
        }

        public void addToOccurrenceCount(Integer toAdd){
            occurrenceCount += toAdd;
        }

        public void setFirstOccurrence(Integer firstOcc){
            firstOccurrence = new Integer(firstOcc);
        }
    }

Answer 1

正如您所顯示的那樣，您的代碼會生成您提供的正確輸出，而不是您聲稱的錯誤輸出。

這是一個獨立的演示：

https://gist.github.com/4056538