使用流从列表生成映射

Question

List<Person> personList =..;  //pid,personName,personAge;
List<Address> addressList =..;//pid,location,homeAddress;
 
HashMap<String, String> map = new HashMap<>();

personList.stream().filter(..)//how to iterate the second List?

  map.put(pid,location);

Answer 1

流API不对集合进行迭代；相反，它从源创建一个流，您不能从两个不同的资源创建一个流。

您可以使用一种规避方法，这将实现您所希望的：

List<Person> personList = ...;  //pid, personName, personAge;
List<Address> addressList = ...;//pid, location, homeAddress;

HashMap<String, String> map = new HashMap<>();

//get the size of smaller list, as lists are of different sizes.
int size = Math.min(personList.size(), addressList.size());

IntStream.range(0, size)
        .mapToObj(e -> new SimpleEntry<>(personList.get(e).getPid(), addressList.get(e).getLocation()))
        .forEach(e -> map.put(e.getKey(), e.getValue()));

备注：

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