Java Collections.sort（）沒有比較元素

Question

我有一個IndexList的ArrayList，它是一個帶有字符串的簡單類，以及兩個整數和下面顯示的compareTo()方法。我的問題是，當我在ArrayList上調用Collections.sort()時，大多數情況下所有的排序都是正確的，但有時候兩個元素永遠不會進行比較，導致排序錯誤。

一些供參考代碼：

//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; 
     } 
    } 
} 

這裏是所有IndexEntry的字母「C」的一些輸出例如：如何發生次數和初次發生後，被確定爲

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 

公告是一樣的，它停止排序。正確的輸出是：

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 

不管怎麼說，就像我說的我都省略了大量的信息，但如果有的話，想到我會很感激的想法。事實上，在創建ArrayList之後，「匹配」數據結構不會被修改。編輯： 嘿，我還在閱讀你的迴應。非常感謝您的快速幫助！這裏是整個IndexEntry類，因爲你們幾個問：

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

你的代碼，因爲你展示它，會產生你給是正確的，而不是你要求它做的不正確輸出的輸出。

下面是一個自包含演示：

https://gist.github.com/4056538