Tue, 13 Jun 2017 16:30:24 -0700
Added tag jdk8u151-b01 for changeset 681ab42e7c73
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 list_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.util.ArrayLists.
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 ArrayList = Java.type("java.util.ArrayList");
43 var list = new ArrayList();
44 list.add("nashorn");
45 list.add("ecmascript");
46 list.add("javascript");
47 list.add("js");
48 list.add("scheme");
50 var map = Array.prototype.map;
51 var filter = Array.prototype.filter;
52 var reduce = Array.prototype.reduce;
54 // sum of word lengths
55 print("Sum word length:",
56 reduce.call(
57 map.call(list, function(x) x.length),
58 function(x, y) x + y)
59 );
61 // filter use to filter out "j*" and concatenate rest with ":"
62 // after uppercasing all strings
63 print(
64 reduce.call(
65 map.call(
66 filter.call(list, function(x) !x.startsWith("j")),
67 function(x) x.toUpperCase()),
68 function(x, y) x + ":" + y)
69 );
71 // another list example involving numbers
72 list.clear();
73 // make random list of numbers
74 for (var i = 0; i < 10; i++)
75 list.add(Math.random());
77 var forEach = Array.prototype.forEach;
78 // print numbers in the list
79 forEach.call(list, function(x) print(x));
81 // print sum of squares of the random numbers
82 print("Square sum:",
83 reduce.call(
84 map.call(list, function(x) x*x),
85 function(x, y) x + y)
86 );