[英]Java8: Map<X, Y> to Map<X, Z> using RxJava
I know how to transform Map<X, Y>
to Map<X, Z>
using stream and it there was also a previous question about this. 我知道如何使用流将
Map<X, Y>
为Map<X, Z>
,之前还有一个关于此的问题 。
But I want to learn how do it using RxJava. 但我想学习如何使用RxJava。
And to be more specific: 更具体一点:
//Input:
Map<String,String> in; // map from key to a string number, for example: "10"
//transform: in -> out
//Output:
Map<String,Integer> out; //map from the same key to Integer.parseInt(val) (invariant: val is a string number)
I think Dávid Karnok is right in a sense that it is not particularly useful case for RxJava if your only goal is to convert a single map. 我认为DávidKarnok在某种意义上是正确的,如果你的唯一目标是转换单个地图,那么它对RxJava来说并不是特别有用。 It might make more sense if you have Observable of (multiple) maps.
如果您有(多个)地图的Observable可能会更有意义。
Then I would recommend to use a convenience of Guava transformers: https://google.github.io/guava/releases/snapshot/api/docs/com/google/common/collect/Maps.html#transformValues(java.util.Map,%20com.google.common.base.Function) 然后我建议使用方便的Guava变换器: https ://google.github.io/guava/releases/snapshot/api/docs/com/google/common/collect/Maps.html#transformValues(java.util 。地图,%20com.google.common.base.Function)
Map<String,String> source1 = ...
Map<String,String> source2 = ...
Observable.just(source1, source2)
.map(map->Maps.transformValues(map, v->Integer.parseInt(v)));
One nice thing about Guava's map value transformer is that it does not recreate map data structure, but instead creates a transformed view which maps values lazily (on the fly). 关于Guava的地图值变换器的一个好处是它不会重新创建地图数据结构,而是创建一个变换的视图,它可以懒惰地(动态地)映射值。
If you do not want to depend on Guava, you can just trivially implement Func1<Map<String,String>,Map<String,Integer>>
yourself. 如果你不想依赖Guava,你可以自己轻松地实现
Func1<Map<String,String>,Map<String,Integer>>
。
You can use Observable.toMap
. 您可以使用
Observable.toMap
。
I think this is a minimal example: 我认为这是一个最小的例子:
Map<String, String> test = new HashMap<String, String>() {
{
put("1", "1");
put("2", "2");
}
};
Map<String, Integer> res = Observable.from(test.entrySet()).toMap(e -> e.getKey(), e -> Integer.parseInt(e.getValue())).toBlocking().first();
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