如何獲得兩個地圖Java之間的區別？

Question

我有兩個圖如下：

Map<String, Record> sourceRecords; 
Map<String, Record> targetRecords; 

我想拿到鑰匙從每個maps.i.e.的不同

1. 它顯示了在sourceRecords中可用但在targetRecords中沒有的映射鍵。
2. 它顯示了在targetRecords中可用但不在sourceRecords中的映射鍵。

我做到了，如下：

Set<String> sourceKeysList = new HashSet<String>(sourceRecords.keySet()); 
Set<String> targetKeysList = new HashSet<String>(targetRecords.keySet()); 

SetView<String> intersection = Sets.intersection(sourceKeysList, targetKeysList); 
Iterator it = intersection.iterator(); 
while (it.hasNext()) { 
    Object object = (Object) it.next(); 
    System.out.println(object.toString()); 
} 

SetView<String> difference = Sets.symmetricDifference(sourceKeysList, targetKeysList); 
ImmutableSet<String> immutableSet = difference.immutableCopy(); 

編輯

if(sourceKeysList.removeAll(targetKeysList)){ 
      //distinct sourceKeys 
      Iterator<String> it1 = sourceKeysList.iterator(); 
      while (it1.hasNext()) { 
       String id = (String) it1.next(); 
       String resultMessage = "This ID exists in source file but not in target file"; 
       System.out.println(resultMessage); 
       values = createMessageRow(id, resultMessage); 
       result.add(values); 
      } 
     } 
     if(targetKeysList.removeAll(sourceKeysList)){ 
      //distinct targetKeys 
      Iterator<String> it1 = targetKeysList.iterator(); 
      while (it1.hasNext()) { 
       String id = (String) it1.next(); 
       String resultMessage = "This ID exists in target file but not in source file"; 
       System.out.println(resultMessage); 
       values = createMessageRow(id, resultMessage); 
       result.add(values); 
      } 
     } 

我能找到共同的密鑰而不是不同的鍵。請幫忙。

Answer 1

套件允許您將刪除元素。

如果產生 「幫手」 規定是不是對你的問題（因爲太多的條目;怎麼樣：

Set<String> sources = get a copy of all source entries 
Set<String> targets = get a copy of all source entries 

則：

sources.removeAll(targets) ... leaves only entries in sources that are only in sources, not in target 

而

sources.retainAll(targets) ... leaves only entries that are in both sets 

你可以從這裏開始工作...

Answer 2

您可以使用複製Set和removeAll：

Set<String> difference = new HashSet<String>(sourceKeysList); 
difference.removeAll(targetKeysList); 

見The Set Interface

Answer 3

1. 它顯示sourceRecords可用，但不是在targetRecords映射按鍵。

sourceKeysList.removeAll(targetKeysList)

它顯示在targetRecords可用但不是在sourceRecords映射鍵。

targetKeysList.removeAll(sourceKeysList)

Answer 4

您可以使用Guava的Maps.difference(Map<K, V> left, Map<K, V> right)方法。它返回一個MapDifference對象，這對於讓所有4種映射條目的方法：

• 同樣出現在左邊和右邊的地圖
• 只在左側地圖
• 只有在正確的地圖
• 鍵存在
  ：在這兩個地圖，而值不同

所以你的情況，也可能只有3行代碼來解決

MapDifference<String, Record> diff = Maps.difference(sourceRecords, targetRecords); 
Set<String> keysOnlyInSource = diff.entriesOnlyOnLeft().keySet(); 
Set<String> keysOnlyInTarget = diff.entriesOnlyOnRight().keySet();