问题

我有两个数据结构，其值如下：

    List<Map<String, String>> customerDirectory

```java
[{NAME=ALEX BENSON, PHONE=012-12342, ADDRESS=123 MAIN ST, CITY=QUEENS, STATE=NY},
 {NAME=ZOYE ABEL, PHONE=012-12445, ADDRESS=123 WATERSIDE, CITY=WINDSOR, STATE=CT}]

和

Map<String, String> customerInfo

{NAME=ALEX BENSON, PHONE=012-12342, ADDRESS=123 MAIN ST}

我正在尝试遍历customerDirectory，以查找customerInfo的值在键"NAME"，"PHONE"，"ADDRESS"上是否有完全匹配，以便我可以判断记录是否重复。

所以我想到了：

List<String> compareKeys = Arrays.asList("NAME","PHONE","ADDRESS");

Function<Map<String,String>, String> getVal = mp -> compareKeys.stream().map(mp::get).map(String::trim).collect(Collectors.joining());

BiPredicate<Map<String,String>, Map<String,String>> checkDup = (mp1,mp2) -> getVal.apply(mp1).equals(getVal.apply(mp2));

boolean anyMatch = customerDirectory.stream().anyMatch(customer -> checkDup.test(customerInfo, customer));

但是customerInfo映射的ADDRESS键可以具有值为null，我尝试了：

BiFunction<Map<String, String>, String, String> handleNull = (mp, key) -> mp.get(key) == null ? " " : mp.get(key);

并将其用于：

Function<Map<String,String>, String> getVal = mp -> compareKeys.stream().map(key -> handleNull.apply(mp,key)).map(mp::get).map(String::trim).collect(Collectors.joining());

但我仍然会遇到NullPointerException，这意味着我可能在流程中遗漏了一些内容。是否有更好的方法来处理这里的null值？

<details>
<summary>英文:</summary>

I have 2 data structures with values like:

    List&lt;Map&lt;String,String&gt;&gt; customerDirectory

[{NAME=ALEX BENSON, PHONE=012-12342, ADDRESS=123 MAIN ST, CITY=QUEENS, STATE=NY},
{NAME=ZOYE ABEL, PHONE=012-12445, ADDRESS=123 WATERSIDE, CITY=WINDSOR, STATE=CT}]

and

    Map<String,String> customerInfo

{NAME=ALEX BENSON, PHONE=012-12342, ADDRESS=123 MAIN ST}

I am trying to iterate through the `customerDirectory` to find if `customerInfo` has exact match in values for the keys - `"NAME","PHONE","ADDRESS"` so that I could find if the record is a duplicate.

So I have come up with:

    List<String> compareKeys = Arrays.asList("NAME","PHONE","ADDRESS");

    Function<Map<String,String>, String> getVal = mp -> compareKeys.stream().map(mp::get).map(String::trim).collect(Collectors.joining());

    BiPredicate<Map<String,String>, Map<String,String>> checkDup = (mp1,mp2) -> getVal.apply(mp1).equals(getVal.apply(mp2));

    boolean anyMatch = customerDirectory.stream().anyMatch(customer-> checkDup.test(customerInfo, customer));

But the `customerInfo` map can have value for `ADDRESS` as `null` for which I have tried:

    BiFunction<Map<String, String>, String, String> handleNull = (mp, key) -> mp.get(key) == null ? " " : mp.get(key);

and I have used it in :

    Function<Map<String,String>, String> getVal = mp -> compareKeys.stream().map(key->handleNull.apply(mp,key)).map(mp::get).map(String::trim).collect(Collectors.joining());

But I still end up getting `NullPointerException` which means I am missing the exact flow probably.
Is there a better way to handle `null` values here?



</details>


# 答案1
**得分**: 5

如果我正确理解您的问题，那么您只是想找出是否有任何精确匹配，而且您希望将答案保留在 **anyMatch** 中。请尝试使用以下代码进行更新。

```java
Function<Map<String, String>, String> getVal = mp ->
    compareKeys.stream().map(mp::get).filter(Objects::nonNull).map(String::trim)
        .collect(Collectors.joining());

Function<Map<String, String>, String> getVal = mp -> 
    compareKeys.stream().map(mp::get).filter(Objects::nonNull).map(String::trim)
			.collect(Collectors.joining());

答案2

得分: 4

你可以用更好的方式来做，我认为。

boolean anyMatch = customerDirectory.stream()
         .anyMatch(m -> m.entrySet().stream()
           .filter(entry -> compareKeys.contains(entry.getKey()))
           .allMatch(entry -> entry.getValue().equals(customerInfo.get(entry.getKey()))));

甚至更加简洁的写法：

boolean anyMatch =
            customerDirectory.stream()
                   .anyMatch(m -> compareKeys.stream()
                            .allMatch(key -> m.get(key).equals(customerInfo.get(key))));

boolean anyMatch = customerDirectory.stream()
         .anyMatch(m -> m.entrySet().stream()
           .filter(entry -> compareKeys.contains(entry.getKey()))
           .allMatch(entry -> entry.getValue().equals(customerInfo.get(entry.getKey()))));

 boolean anyMatch =
            customerDirectory.stream()
                   .anyMatch(m -> compareKeys.stream()
                            .allMatch(key -> m.get(key).equals(customerInfo.get(key))));