如何获得两个映射Java之间的区别？

Question

我有两张地图如下:

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

我想让每个maps.ie的键都不同

1. 它显示sourceRecords中可用的映射键,但不显示targetRecords中的映射键.
2. 它显示targetRecords中可用的映射键,但不显示sourceRecords中的映射键.

我做了如下:

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();

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);
            }
        }

我能够找到公共密钥但不能找到不同的密钥.请帮忙.

Answer 1

你可以使用番石榴的Maps.difference(Map<K, V> left, Map<K, V> right)方法.它返回一个MapDifference对象,该对象具有获取所有四种映射条目的方法:

• 同样出现在左右地图中
• 只在左图中
• 只在右图中
• 密钥存在于两个映射中,但具有不同的值

因此,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();

Answer 2

集也允许您删除元素.

如果生成"帮助"集对你来说不是问题(因为条目太多;那么:

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

然后:

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

你可以从这里开始工作......

Answer 3

您可以使用副本Set并且removeAll：

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

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