java - 如何获得两个 map Java之间的差异？

Question

我有两张 map 如下:

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

我想获得与每个 map 不同的键。即

1. 它显示在 sourceRecords 中可用但在 targetRecords 中不可用的映射键。
2. 它显示了 targetRecords 中可用但 sourceRecords 中不可用的映射键。

我是这样做的:

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();

编辑

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);
            }
        }

我能够找到通用键但不能找到不同键。请帮忙。

Answer 1

您可以使用 Guava的 Maps.difference(Map<K, V> left, Map<K, V> right) 方法。它返回 MapDifference 对象，它具有获取所有四种映射条目的方法:

• 在左右 map 中均等出现
• 只在左图<​​/li>
• 只在右图
• key 出现在两个映射中，但具有不同的值

所以在您的情况下，只需 3 行代码即可解决:

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