diff -r 000000000000 -r b1a7da25b547 samples/javacastcounter.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/samples/javacastcounter.js	Wed Apr 27 01:36:41 2016 +0800
@@ -0,0 +1,107 @@
+/*
+ * Copyright (c) 2014, 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 javacastcounter.js -- <.java files>
+
+// This example demonstrates Nashorn Java.extend API
+// to subclass a Java class from script.
+
+// This example uses Javac Compiler and Tree API
+// to list type casts used in java source files.
+
+if (arguments.length == 0) {
+    print("Usage: jjs javacastcounter.js -- <.java files>");
+    exit(1);
+}
+
+// Java types used
+var ToolProvider = Java.type("javax.tools.ToolProvider");
+var TreeScanner = Java.type("com.sun.source.util.TreeScanner");
+var Trees = Java.type("com.sun.source.util.Trees");
+var StringArray = Java.type("java.lang.String[]");
+
+// get the system compiler tool
+var compiler = ToolProvider.systemJavaCompiler;
+
+// get standard file manager
+var fileMgr = compiler.getStandardFileManager(null, null, null);
+
+// make a list of compilation unit from command line argument file names
+// 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);
+
+// SourcePositions object to get positions of AST nodes
+var sourcePositions = Trees.instance(task).sourcePositions;
+
+// Subclass TreeScanner class
+var CastCounter = Java.extend(TreeScanner);
+
+var counter = new CastCounter() {
+    // current CompilationUnitTree
+    compUnit: null,
+    // current LineMap (pos -> line, column)
+    lineMap: null,
+    // current compilation unit's file name
+    fileName: null,
+
+    // overrides of TreeScanner methods
+
+    visitCompilationUnit: function(node, p) {
+        // capture info about current Compilation unit
+        this.compUnit = node;
+        this.lineMap = node.lineMap;
+        this.fileName = node.sourceFile.name;
+
+        // Using Java.super API to call super class method here        
+        return Java.super(counter).visitCompilationUnit(node, p);
+    },
+
+    visitTypeCast: function(node, p) {
+        // print information on this type cast node
+        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);
+
+        // count one more type cast
+        return 1;
+    },
+
+    reduce: function(r1, r2) {
+        return (r1 == null ? 0 : r1) + (r2 == null ? 0 : r2);
+    }
+};
+
+// print total number of type cast nodes seen
+print("Total casts:", counter.scan(task.parse(), null));