Github user fobeligi commented on a diff in the pull request: https://github.com/apache/flink/pull/2178#discussion_r68848969 --- Diff: flink-libraries/flink-gelly/src/main/java/org/apache/flink/graph/Graph.java --- @@ -408,6 +408,79 @@ public static GraphCsvReader fromCsvReader(String edgesPath, ExecutionEnvironmen } /** + * Creates a graph from a Adjacency List text file with Vertex Key values. Edges will be created automatically. + * + * @param filePath a path to an Adjacency List text file with the Vertex data + * @param context the execution environment. + * @return An instance of {@link org.apache.flink.graph.GraphAdjacencyListReader}, + * on which calling methods to specify types of the Vertex ID, Vertex value and Edge value returns a Graph. + */ + public static GraphAdjacencyListReader fromAdjacencyListFile(String filePath, ExecutionEnvironment context) { + return new GraphAdjacencyListReader(filePath, context); + } + + /** + * Writes a graph as an Adjacency List formatted text file in a user specified folder. + * + * @param filePath the path that the Adjacency List formatted text file should be written in + * @param delimiters the delimiters that separate the different value types in the Adjacency List formatted text + * file. Delimiters should be provided with the following order: + * NEIGHBOR_DELIMITER : separating source from its neighbors + * VERTICES_DELIMITER : separating the different neighbors of a source vertex + * VERTEX_VALUE_DELIMITER: separating the source vertex-id from the vertex value, as well as the + * target vertex-ids from the edge value. + */ + public void writeAsAdjacencyList(String filePath, String... delimiters) { + + final String NEIGHBOR_DELIMITER = delimiters.length > 0 ? delimiters[0] : "\t"; + + final String VERTICES_DELIMITER = delimiters.length > 1 ? delimiters[1] : ","; + + final String VERTEX_VALUE_DELIMITER = delimiters.length > 1 ? delimiters[2] : "-"; --- End diff -- You mean the error in this declaration: ```java final String VERTEX_VALUE_DELIMITER = delimiters.length > 1 ? delimiters[2] : "-"; ``` and not to check directly for length greater than two, because in that way the user will have to provide all three delimiters or none.
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