java,c#,linq,java-8 , C# + linq(concat) rewrite to java


C# + linq(concat) rewrite to java

Question:

Tag: java,c#,linq,java-8

I have a code example in C# (with linq) but am trying to translate this to java code (java 8). But am getting very confused about what happens. Also i am not able to reproduce the same result in java as from the c# code.

public IEnumerable<Node> GetNeighborNodes(Node v)
{
    var q = (from edge in this.Edges
        where edge.Start == v
        select edge.End)
        .Concat(from edge in this.Edges
            where edge.End == v
            select edge.Start);
    return q;
}

I get very confused by the Concat part. Can anyone explain what happens and how to reproduce this in java ?


Answer:
var q = (from edge in this.Edges
    where edge.Start == v
    select edge.End)
    .Concat(from edge in this.Edges
        where edge.End == v
        select edge.Start);

this is same as

var q = 
  ctx.Edges.Where(o => o.Start == v).Select(o => o.End).Union(
  ctx.Edges.Where(o => o.End == v).Select(o => o.Start)).ToList();

and this would be

Stream<Node> q = Stream.concat(
  this.getEdges().stream().filter(o-> o.getStart() == v).map(o-> o.getEnd()),
  this.getEdges().stream().filter(o-> o.getEnd() == v).map(o-> o.getStart())
);

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