--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/sample/nashorn/find_underscores.js	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,101 @@
+/*
+ * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *   - Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ *
+ *   - Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *
+ *   - Neither the name of Oracle nor the names of its
+ *     contributors may be used to endorse or promote products derived
+ *     from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+ * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+// Usage: jjs find_underscores.js -- <directory>
+
+if (arguments.length == 0) {
+    print("Usage: jjs find_underscores.js -- <directory>");
+    exit(1);
+}
+
+// Java types used
+var File = Java.type("java.io.File");
+var Files = Java.type("java.nio.file.Files");
+var StringArray = Java.type("java.lang.String[]");
+var ToolProvider = Java.type("javax.tools.ToolProvider");
+var Tree = Java.type("com.sun.source.tree.Tree");
+var Trees = Java.type("com.sun.source.util.Trees");
+var TreeScanner = Java.type("com.sun.source.util.TreeScanner");
+
+function findUnderscores() {
+    // get the system compiler tool
+    var compiler = ToolProvider.systemJavaCompiler;
+    // get standard file manager
+    var fileMgr = compiler.getStandardFileManager(null, null, null);
+    // Using Java.to convert script array (arguments) to a Java String[]
+    var compUnits = fileMgr.getJavaFileObjects(Java.to(arguments, StringArray));
+    // create a new compilation task
+    var task = compiler.getTask(null, fileMgr, null, null, null, compUnits);
+    var sourcePositions = Trees.instance(task).sourcePositions;
+    // subclass SimpleTreeVisitor - to find underscore variable names
+    var UnderscoreFinder = Java.extend(TreeScanner);
+
+    var visitor = new UnderscoreFinder() {
+        // override to capture information on current compilation unit
+        visitCompilationUnit: function(compUnit, p) {
+            this.compUnit = compUnit;
+            this.lineMap = compUnit.lineMap;
+            this.fileName = compUnit.sourceFile.name;
+
+            return Java.super(visitor).visitCompilationUnit(compUnit, p);
+        },
+
+        // override to check variable name
+        visitVariable: function(node, p) {
+            if (node.name.toString() == "_") {
+                var pos = sourcePositions.getStartPosition(this.compUnit, node);
+                var line = this.lineMap.getLineNumber(pos);
+                var col = this.lineMap.getColumnNumber(pos);
+                print(node + " @ " + this.fileName + ":" + line + ":" + col);
+            }
+
+            return Java.super(visitor).visitVariable(node, p);
+        }
+    }
+
+    for each (var cu in task.parse()) {
+        cu.accept(visitor, null);
+    }
+}
+
+// for each ".java" file in directory (recursively).
+function main(dir) {
+    var totalCount = 0;
+    Files.walk(dir.toPath()).
+      forEach(function(p) {
+          var name = p.toFile().absolutePath;
+          if (name.endsWith(".java")) {
+              findUnderscores(p);
+          }
+      });
+}
+
+main(new File(arguments[0]));