Mon, 09 Nov 2015 13:45:10 -0800
Merge
1 /*
2 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 *
8 * - Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 *
11 * - Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * - Neither the name of Oracle nor the names of its
16 * contributors may be used to endorse or promote products derived
17 * from this software without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
20 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
21 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
23 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
24 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
25 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
26 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
27 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
28 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
29 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30 */
32 // Usage: jjs array_mapreduce.js
34 // Many Array.prototype functions such as map,
35 // filter, reduce, reduceRight, every, some are generic.
36 // These functions accept ECMAScript array as well as
37 // many array-like objects including java arrays.
38 // So, you can do map/filter/reduce with Java streams or
39 // you can also use Array.prototype functions as below.
40 // See also http://en.wikipedia.org/wiki/MapReduce
42 var DoubleArray = Java.type("double[]");
43 var StringArray = Java.type("java.lang.String[]");
45 var map = Array.prototype.map;
46 var filter = Array.prototype.filter;
47 var reduce = Array.prototype.reduce;
49 var jarr = new StringArray(5);
50 jarr[0] = "nashorn";
51 jarr[1] = "ecmascript";
52 jarr[2] = "javascript";
53 jarr[3] = "js";
54 jarr[4] = "scheme";
56 // sum of word lengths
57 print("Sum word length:",
58 reduce.call(
59 map.call(jarr, function(x) x.length),
60 function(x, y) x + y)
61 );
63 // another array example involving numbers
64 jarr = new DoubleArray(10);
65 // make random array of numbers
66 for (var i = 0; i < jarr.length; i++)
67 jarr[i] = Math.random();
69 var forEach = Array.prototype.forEach;
70 // print numbers in the array
71 forEach.call(jarr, function(x) print(x));
73 // print sum of squares of the random numbers
74 print("Square sum:",
75 reduce.call(
76 map.call(jarr, function(x) x*x),
77 function(x, y) x + y)
78 );