Java流<Object>过滤然后使用结果

Question

I don't understand how to use the results of filtering a Stream<>. Example:

Stream<Edge> edgesStr = graph.edges().filter(edge -> edge.getNode1() == graph.getNode(ip2));

The above successfully(?) filters the Edge stream, keeping only those edges where the getNode() methods are equal. Now after this, I want to use those results, something like:

//for each result
Node node = edgeStr.getNode(); //method getNode() exists for objects Edge
foo1(Node);
foo2(Node);

Note: graph.edges() returns a Stream<Edges> .

Answer 1

You can collect the results via some of the Collector methods, ie toList when collecting into a List . In order to extract the Node out of the Edge you can use map .

List<Node> edges = graph.edges()
    .filter(edge -> edge.getNode1() == graph.getNode(ip2))
    .map(edge -> edge.getNode())
    .collect(Collectors.toList());

Answer 2

If you need to perform void operations foo1 and foo2 on a Node element, for each edge, you can do it as:

graph.edges()
     .filter(edge -> edge.getNode() == graph.getNode(ip2))
     .map(edge -> edge.getNode()) // map edge to corresponding Node
     .forEach(node -> { foo1(node); foo2(node);}); // calls foo1 and foo2 on each node