java 如何使用 Lambda 表达式填充 HashMap
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/29207744/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
How to populate a HashMap using a Lambda Expression
提问by Paramesh Korrakuti
There is one class (SomeOrders), which has few fields like Id, Summary, Amount, etc...
还有一类（SomeOrders），它具有像几个字段Id，Summary，Amount，等...
The requirement is to collect Idas key and Summaryas value to a HashMapfrom an input Listof SomeOrderobjects.
要求是从对象输入中Id作为键和Summary值收集到 a 。HashMapListSomeOrder
Code in Before java 8:
java 8之前的代码：
List<SomeOrder> orders = getOrders();
Map<String, String> map = new HashMap<>();
for (SomeOrder order : orders) {
map.put(order.getId(), order.getSummary());
}
How to achieve the same with Lambda expression in Java 8?
如何在 Java 8 中使用 Lambda 表达式实现相同的目标？
回答by Eran
Use Collectors.toMap:
使用Collectors.toMap：
orders.stream().collect(Collectors.toMap(SomeOrder::getID, SomeOrder::getSummary));
or
或者
orders.stream().collect(Collectors.toMap(o -> o.getID(), o -> o.getSummary()));
