[英]Java 8 Stream API Collector Issue
I'm traversing a graph by its edges and want to have a list of all sources and targets. 我正在遍历图形的边缘,并希望得到所有源和目标的列表。 This is what I have so far:
这是我到目前为止:
public Set<Vertex> getVertices(){
Set<Vertex> vertices = this.edges.stream().map(edge -> edge.getSource()).collect(Collectors.toSet());
vertices.addAll(this.edges.stream().map(edge -> edge.getTarget()).collect(Collectors.toSet()));
return vertices;
}
Is there any way to get both source and target in the same mapping/collection step? 有没有办法在同一个映射/收集步骤中获取源和目标? Something like (PSEUDO-CODE):
像(PSEUDO-CODE)这样的东西:
edges.stream().collect(edge.getSource()).collect(edge.getTarget())
Or plain old Java 7 或普通的旧Java 7
for ( Edge e : edges ){
vertices.add(e.getSource());
vertices.add(e.getTarget());
}
Cheers, Daniel 干杯,丹尼尔
Set<Vertex> vertices = edges.stream()
.flatMap(e -> Stream.of(e.getSource(), e.getTarget()))
.collect(Collectors.toSet());
Yoy can use Misha's suggestion or write the collector manually: Yoy可以使用Misha的建议或手动编写收集器:
Set<String> vertices = this.edges.stream()
.collect(HashSet::new, (set, edge) -> {
set.add(edge.getSource());
set.add(edge.getTarget());
}, Set::addAll);
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