Move all find methods into graphFinder.

apm-collector/apm-collector-core/src/main/java/org/skywalking/apm/collector/core/graph/Graph.java

@@ -43,16 +43,6 @@ public final class Graph<INPUT> {
         }
     }
 
-    public Next findNext(int handlerId) {
-        Node node = nodeIndex.get(handlerId);
-        if (node == null) {
-            throw new NodeNotFoundException("Can't find node with handlerId="
-                + handlerId
-                + " in graph[" + id + "]");
-        }
-        return node.getNext();
-    }
-
     void checkForNewNode(Node node) {
         int nodeId = node.getHandler().id();
         if (nodeIndex.containsKey(nodeId)) {
@@ -63,11 +53,15 @@ public final class Graph<INPUT> {
         nodeIndex.put(nodeId, node);
     }
 
-    public GraphBuilder toBuilder(){
-        return new GraphBuilder(this);
+    public GraphNodeFinder toFinder() {
+        return new GraphNodeFinder(this);
     }
 
     ConcurrentHashMap<Integer, Node> getNodeIndex() {
         return nodeIndex;
     }
+
+    int getId() {
+        return id;
+    }
 }

apm-collector/apm-collector-core/src/main/java/org/skywalking/apm/collector/core/graph/GraphNodeFinder.java

@@ -23,21 +23,40 @@ import java.util.concurrent.ConcurrentHashMap;
 /**
  * @author wu-sheng
  */
-public class GraphBuilder {
+public class GraphNodeFinder {
     private Graph graph;
 
-    GraphBuilder(Graph graph) {
+    GraphNodeFinder(Graph graph) {
         this.graph = graph;
     }
 
+    /**
+     * Find an exist node to build the graph.
+     *
+     * @param handlerId of specific node in graph.
+     * @param outputClass of the found node
+     * @param <NODE_OUTPUT> type of given output class
+     * @return Node instance.
+     */
     public <NODE_OUTPUT> Node<?, NODE_OUTPUT> findNode(int handlerId, Class<NODE_OUTPUT> outputClass) {
         ConcurrentHashMap<Integer, Node> graphNodeIndex = graph.getNodeIndex();
         Node node = graphNodeIndex.get(handlerId);
         if (node == null) {
             throw new NodeNotFoundException("Can't find node with handlerId="
                 + handlerId
-                + " in graph[" + handlerId + "]");
+                + " in graph[" + graph.getId() + "]");
         }
         return node;
     }
+
+    public Next findNext(int handlerId) {
+        ConcurrentHashMap<Integer, Node> graphNodeIndex = graph.getNodeIndex();
+        Node node = graphNodeIndex.get(handlerId);
+        if (node == null) {
+            throw new NodeNotFoundException("Can't find node with handlerId="
+                + handlerId
+                + " in graph[" + graph.getId() + "]");
+        }
+        return node.getNext();
+    }
 }

apm-collector/apm-collector-core/src/test/java/org/skywalking/apm/collector/core/graph/GraphManagerTest.java

@@ -87,7 +87,7 @@ public class GraphManagerTest {
         Graph<String> graph = GraphManager.INSTANCE.createIfAbsent(4, String.class);
         graph.addNode(new Node1Processor()).addNext(new Node2Processor()).addNext(new Node4Processor());
 
-        Next next = GraphManager.INSTANCE.findGraph(4).findNext(2);
+        Next next = GraphManager.INSTANCE.findGraph(4).toFinder().findNext(2);
 
         next.execute(123);
         String output = outputStream.toString();
@@ -102,7 +102,7 @@ public class GraphManagerTest {
         Graph<String> graph = GraphManager.INSTANCE.createIfAbsent(5, String.class);
         graph.addNode(new Node1Processor()).addNext(new Node2Processor()).addNext(new Node4Processor());
 
-        Next next = GraphManager.INSTANCE.findGraph(5).findNext(3);
+        Next next = GraphManager.INSTANCE.findGraph(5).toFinder().findNext(3);
     }
 
     @Test
@@ -110,7 +110,7 @@ public class GraphManagerTest {
         Graph<String> graph = GraphManager.INSTANCE.createIfAbsent(6, String.class);
         graph.addNode(new Node1Processor()).addNext(new Node2Processor());
 
-        Node<?, Integer> foundNode = GraphManager.INSTANCE.findGraph(6).toBuilder().findNode(2, Integer.class);
+        Node<?, Integer> foundNode = GraphManager.INSTANCE.findGraph(6).toFinder().findNode(2, Integer.class);
         foundNode.addNext(new Node4Processor());
     }