1 files changed, 43 insertions, 0 deletions
diff --git a/container-di/src/main/java/com/yahoo/container/di/componentgraph/cycle/Graph.java b/container-di/src/main/java/com/yahoo/container/di/componentgraph/cycle/Graph.java
new file mode 100644
index 00000000000..e1b110d51ee
--- /dev/null
+++ b/container-di/src/main/java/com/yahoo/container/di/componentgraph/cycle/Graph.java
@@ -0,0 +1,43 @@
+/*
+ * Copyright 2019 Oath Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+ */
+
+package com.yahoo.container.di.componentgraph.cycle;
+
+import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * Class representing a directed graph.
+ *
+ * @author gjoranv
+ */
+public class Graph<T> {
+
+    private final Map<T, LinkedHashSet<T>> adjMap = new LinkedHashMap<>();
+
+    public void edge(T from, T to) {
+        if (from == null || to == null)
+            throw new IllegalArgumentException("Null vertices are not allowed, edge: " + from + "->" + to);
+
+        adjMap.computeIfAbsent(from, k -> new LinkedHashSet<>()).add(to);
+        adjMap.computeIfAbsent(to, k -> new LinkedHashSet<>());
+    }
+
+    Set<T> getVertices() {
+        return adjMap.keySet();
+    }
+
+    /**
+     * Returns the outgoing edges of the given vertex.
+     */
+    Set<T> getAdjacent(T vertex) {
+        return adjMap.get(vertex);
+    }
+
+    private void throwIfMissingVertex(T vertex) {
+        if (! adjMap.containsKey(vertex)) throw new IllegalArgumentException("No such vertex in the graph: " + vertex);
+    }
+}