Mercurial > jdk8-mips64-public > nashorn / file revision

 /*

  * 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,

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  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR

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 // Usage: jjs list_mapreduce.js

 // Many Array.prototype functions such as map, 

 // filter, reduce, reduceRight, every, some are generic.

 // These functions accept ECMAScript array as well as 

 // many array-like objects including java.util.ArrayLists.

 // So, you can do map/filter/reduce with Java streams or

 // you can also use Array.prototype functions as below.

 // See also http://en.wikipedia.org/wiki/MapReduce

 var ArrayList = Java.type("java.util.ArrayList");

 var list = new ArrayList();

 list.add("nashorn");

 list.add("ecmascript");

 list.add("javascript");

 list.add("js");

 list.add("scheme");

 var map = Array.prototype.map;

 var filter = Array.prototype.filter;

 var reduce = Array.prototype.reduce;

 // sum of word lengths

 print("Sum word length:",

     reduce.call(

         map.call(list, function(x) x.length),

         function(x, y) x + y)

 );

 // filter use to filter out "j*" and concatenate rest with ":"

 // after uppercasing all strings

 print(

     reduce.call(

         map.call(

             filter.call(list, function(x) !x.startsWith("j")),

             function(x) x.toUpperCase()),

         function(x, y) x + ":" + y)

 );

 // another list example involving numbers

 list.clear();

 // make random list of numbers

 for (var i = 0; i < 10; i++)

     list.add(Math.random());

 var forEach = Array.prototype.forEach;

 // print numbers in the list

 forEach.call(list, function(x) print(x));

 // print sum of squares of the random numbers

 print("Square sum:",

     reduce.call(

         map.call(list, function(x) x*x), 

         function(x, y) x + y)

 );