如何转换List <NameValuePair> 进入hashMap <String, String> ？

Question

I'm capturing parameters from a request url using com.apache.http.NameValuePair which basically store those params in List<NameValuePair> . To do certain checks and verifications on those params, I need to convert that list into a HashMap<String, String> . Is there a way to do this conversion?

Answer 1

Do you use Java 8? In that case you could make use of the Collectors.toMap() method:

Map<String, String> mapped = list.stream().collect(
        Collectors.toMap(NameValuePair::getName, NameValuePair::getValue));

Otherwise you would have to loop through the elements

for(NameValuePair element : list) {
  //logic to convert list entries to hash map entries
}

To get a better understanding, please take a look at this tutorial .

Answer 2

You can use it for Java 8

public static <K, V, T extends V> Map<K, V> toMapBy(List<T> list,
        Function<? super T, ? extends K> mapper) {
    return list.stream().collect(Collectors.toMap(mapper, Function.identity()));
}

And here's how you would use it on a List:

Map<Long, Product> productsById = toMapBy(products, Product::getId);

Follow the link:

1. Converting ArrayList to HashMap
2. Generic static method constrains types too much
3. Java: How to convert List to Map