this.representation = Preconditions.checkNotNull(representation);
this.sourceIdentifier = Preconditions.checkNotNull(sourceIdentifier);
Preconditions.checkArgument(cost >= 0, "cost has to be non-negative");
this.cost = cost;
}
this.representation = Preconditions.checkNotNull(representation);
this.sourceIdentifier = Preconditions.checkNotNull(sourceIdentifier);
Preconditions.checkArgument(cost >= 0, "cost has to be non-negative");
this.cost = cost;
}