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// 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));