Why streams cannot be created for map in Java8?

Question

为什么我们不能为地图创建流 ？

Answer 1

Streams cannot directly be created from maps because a map is not a collection. For further explanation on why a map is not a collection you can view this answer https://stackoverflow.com/a/2651833/2796463 .

Maps in Java can be iterated in three ways:

1. A set of keys
2. A collection of values
3. A a set of key value pairs

You need to specify which order you wish to iterate through the map before creating a stream

1. map.keySet().stream()
2. map.values().stream()
3. map.entrySet().stream()