# HG changeset patch
# User martin
# Date 1522105394 25200
#      Mon Mar 26 16:03:14 2018 -0700
# Node ID 5291c97b4d0002c161d039d7715119b6e0419e72
# Parent  9e84094f43256d848d43ee8429eec4c999368f05
8200134: Improve ModuleHashesBuilder.dfs()
Reviewed-by: alanb

diff --git a/src/java.base/share/classes/jdk/internal/module/ModuleHashesBuilder.java b/src/java.base/share/classes/jdk/internal/module/ModuleHashesBuilder.java
--- a/src/java.base/share/classes/jdk/internal/module/ModuleHashesBuilder.java
+++ b/src/java.base/share/classes/jdk/internal/module/ModuleHashesBuilder.java
@@ -35,7 +35,6 @@
 import java.util.Deque;
 import java.util.HashMap;
 import java.util.HashSet;
-import java.util.LinkedList;
 import java.util.Map;
 import java.util.Set;
 import java.util.function.Consumer;
@@ -78,10 +77,8 @@
         Graph.Builder<String> builder = new Graph.Builder<>();
         Deque<ResolvedModule> deque = new ArrayDeque<>(configuration.modules());
         Set<ResolvedModule> visited = new HashSet<>();
-        while (!deque.isEmpty()) {
-            ResolvedModule rm = deque.pop();
-            if (!visited.contains(rm)) {
-                visited.add(rm);
+        for (ResolvedModule rm; (rm = deque.poll()) != null; ) {
+            if (visited.add(rm)) {
                 builder.addNode(rm.name());
                 for (ResolvedModule dm : rm.reads()) {
                     if (!visited.contains(dm)) {
@@ -212,17 +209,13 @@
          * Returns all nodes reachable from the given set of roots.
          */
         public Set<T> dfs(Set<T> roots) {
-            Deque<T> deque = new LinkedList<>(roots);
-            Set<T> visited = new HashSet<>();
-            while (!deque.isEmpty()) {
-                T u = deque.pop();
-                if (!visited.contains(u)) {
-                    visited.add(u);
-                    if (contains(u)) {
-                        adjacentNodes(u).stream()
-                            .filter(v -> !visited.contains(v))
-                            .forEach(deque::push);
-                    }
+            ArrayDeque<T> deque = new ArrayDeque<>(roots);
+            HashSet<T> visited = new HashSet<>();
+            for (T u; (u = deque.poll()) != null; ) {
+                if (visited.add(u) && contains(u)) {
+                    adjacentNodes(u).stream()
+                        .filter(v -> !visited.contains(v))
+                        .forEach(deque::push);
                 }
             }
             return visited;
@@ -240,11 +233,9 @@
             final Map<T, Set<T>> edges = new HashMap<>();
 
             public void addNode(T node) {
-                if (nodes.contains(node)) {
-                    return;
+                if (nodes.add(node)) {
+                    edges.computeIfAbsent(node, _e -> new HashSet<>());
                 }
-                nodes.add(node);
-                edges.computeIfAbsent(node, _e -> new HashSet<>());
             }
 
             public void addEdge(T u, T v) {
@@ -263,13 +254,13 @@
      * Topological sort
      */
     private static class TopoSorter<T> {
-        final Deque<T> result = new LinkedList<>();
+        final Deque<T> result = new ArrayDeque<>();
         final Deque<T> nodes;
         final Graph<T> graph;
 
         TopoSorter(Graph<T> graph) {
             this.graph = graph;
-            this.nodes = new LinkedList<>(graph.nodes);
+            this.nodes = new ArrayDeque<>(graph.nodes);
             sort();
         }
 
@@ -282,8 +273,8 @@
         }
 
         private void sort() {
-            Deque<T> visited = new LinkedList<>();
-            Deque<T> done = new LinkedList<>();
+            Deque<T> visited = new ArrayDeque<>();
+            Deque<T> done = new ArrayDeque<>();
             T node;
             while ((node = nodes.poll()) != null) {
                 if (!visited.contains(node)) {