| /* |
| * 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 |
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| * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
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| * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| // Usage: jjs array_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 arrays. |
| // 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 DoubleArray = Java.type("double[]"); |
| var StringArray = Java.type("java.lang.String[]"); |
| |
| var map = Array.prototype.map; |
| var filter = Array.prototype.filter; |
| var reduce = Array.prototype.reduce; |
| |
| var jarr = new StringArray(5); |
| jarr[0] = "nashorn"; |
| jarr[1] = "ecmascript"; |
| jarr[2] = "javascript"; |
| jarr[3] = "js"; |
| jarr[4] = "scheme"; |
| |
| // sum of word lengths |
| print("Sum word length:", |
| reduce.call( |
| map.call(jarr, function(x) x.length), |
| function(x, y) x + y) |
| ); |
| |
| // another array example involving numbers |
| jarr = new DoubleArray(10); |
| // make random array of numbers |
| for (var i = 0; i < jarr.length; i++) |
| jarr[i] = Math.random(); |
| |
| var forEach = Array.prototype.forEach; |
| // print numbers in the array |
| forEach.call(jarr, function(x) print(x)); |
| |
| // print sum of squares of the random numbers |
| print("Square sum:", |
| reduce.call( |
| map.call(jarr, function(x) x*x), |
| function(x, y) x + y) |
| ); |