add traversal of the file tree

core/src/main/groovy/com/muwire/core/files/FileTree.groovy

@@ -46,6 +46,31 @@ class FileTree<T> {
         true
     }    
     
+    synchronized void traverse(FileTreeCallback<T> callback) {
+        doTraverse(root, callback);
+    }
+    
+    private void doTraverse(TreeNode<T> node, FileTreeCallback<T> callback) {
+        println "traversing $node"
+        boolean leave = false
+        if (node.file != null) {
+            println "file is $node.file"
+            if (node.file.isFile())
+                callback.onFile(node.file, node.value)
+            else {
+                leave = true
+                callback.onDirectoryEnter(node.file)
+            }
+        }
+        
+        node.children.each { 
+            doTraverse(it, callback)
+        }        
+        
+        if (leave)
+            callback.onDirectoryLeave()
+    }
+    
     public static class TreeNode<T> {
         TreeNode parent
         File file
@@ -53,7 +78,7 @@ class FileTree<T> {
         final Set<TreeNode> children = new HashSet<>()
         
         public int hashCode() {
-            file.hashCode()
+            Objects.hash(file)
         }
         
         public boolean equals(Object o) {

core/src/main/groovy/com/muwire/core/files/FileTreeCallback.java

@@ -0,0 +1,9 @@
+package com.muwire.core.files;
+
+import java.io.File;
+
+public interface FileTreeCallback<T> {
+    public void onDirectoryEnter(File file);
+    public void onDirectoryLeave();
+    public void onFile(File file, T value);
+}

core/src/test/groovy/com/muwire/core/files/FileTreeTest.groovy

@@ -39,4 +39,54 @@ class FileTreeTest {
         tree.remove(d)
         assert tree.fileToNode.size() == 3
     }
+    
+    @Test
+    public void testTraverse() {
+        Stack stack = new Stack()
+        Set<String> values = new HashSet<>()
+        StringBuilder sb = new StringBuilder()
+        def cb = new FileTreeCallback<String>() {
+
+            @Override
+            public void onDirectoryEnter(File file) {
+                stack.push(file)
+            }
+
+            @Override
+            public void onDirectoryLeave() {
+                stack.pop()
+            }
+
+            @Override
+            public void onFile(File file, String value) {
+                values.add(value)
+            }
+        }
+        
+        File a = new File("a")
+        a.createNewFile()
+        File b = new File("b")
+        b.mkdir()
+        File c = new File(b, "c")
+        c.createNewFile()
+        File d = new File(b, "d")
+        d.mkdir()
+        File e = new File(d, "e")
+        e.createNewFile()
+        FileTree<String> tree = new FileTree<>()
+        
+        tree.add(a, "a")
+        tree.add(b, "b")
+        tree.add(c, "c")
+        tree.add(d, "d")
+        tree.add(e, "e")
+        
+        tree.traverse(cb)
+
+        assert stack.isEmpty()
+        assert values.size() == 3
+        assert values.contains("a")
+        assert values.contains("c")
+        assert values.contains("e")
+    }
 }