Wed, 07 Oct 2015 10:01:40 -0700
Merge
aoqi@0 | 1 | /* |
aoqi@0 | 2 | * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved. |
attila@962 | 3 | * |
aoqi@0 | 4 | * Redistribution and use in source and binary forms, with or without |
aoqi@0 | 5 | * modification, are permitted provided that the following conditions |
aoqi@0 | 6 | * are met: |
attila@962 | 7 | * |
aoqi@0 | 8 | * - Redistributions of source code must retain the above copyright |
aoqi@0 | 9 | * notice, this list of conditions and the following disclaimer. |
attila@962 | 10 | * |
aoqi@0 | 11 | * - Redistributions in binary form must reproduce the above copyright |
aoqi@0 | 12 | * notice, this list of conditions and the following disclaimer in the |
aoqi@0 | 13 | * documentation and/or other materials provided with the distribution. |
attila@962 | 14 | * |
aoqi@0 | 15 | * - Neither the name of Oracle nor the names of its |
aoqi@0 | 16 | * contributors may be used to endorse or promote products derived |
aoqi@0 | 17 | * from this software without specific prior written permission. |
attila@962 | 18 | * |
aoqi@0 | 19 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS |
aoqi@0 | 20 | * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, |
aoqi@0 | 21 | * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
aoqi@0 | 22 | * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR |
aoqi@0 | 23 | * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, |
aoqi@0 | 24 | * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
aoqi@0 | 25 | * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR |
aoqi@0 | 26 | * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF |
aoqi@0 | 27 | * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING |
aoqi@0 | 28 | * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS |
aoqi@0 | 29 | * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
aoqi@0 | 30 | */ |
aoqi@0 | 31 | |
aoqi@0 | 32 | // Usage: jjs list_mapreduce.js |
aoqi@0 | 33 | |
attila@962 | 34 | // Many Array.prototype functions such as map, |
aoqi@0 | 35 | // filter, reduce, reduceRight, every, some are generic. |
attila@962 | 36 | // These functions accept ECMAScript array as well as |
aoqi@0 | 37 | // many array-like objects including java.util.ArrayLists. |
aoqi@0 | 38 | // So, you can do map/filter/reduce with Java streams or |
aoqi@0 | 39 | // you can also use Array.prototype functions as below. |
aoqi@0 | 40 | // See also http://en.wikipedia.org/wiki/MapReduce |
aoqi@0 | 41 | |
aoqi@0 | 42 | var ArrayList = Java.type("java.util.ArrayList"); |
aoqi@0 | 43 | var list = new ArrayList(); |
aoqi@0 | 44 | list.add("nashorn"); |
aoqi@0 | 45 | list.add("ecmascript"); |
aoqi@0 | 46 | list.add("javascript"); |
aoqi@0 | 47 | list.add("js"); |
aoqi@0 | 48 | list.add("scheme"); |
aoqi@0 | 49 | |
aoqi@0 | 50 | var map = Array.prototype.map; |
aoqi@0 | 51 | var filter = Array.prototype.filter; |
aoqi@0 | 52 | var reduce = Array.prototype.reduce; |
aoqi@0 | 53 | |
aoqi@0 | 54 | // sum of word lengths |
aoqi@0 | 55 | print("Sum word length:", |
aoqi@0 | 56 | reduce.call( |
aoqi@0 | 57 | map.call(list, function(x) x.length), |
aoqi@0 | 58 | function(x, y) x + y) |
aoqi@0 | 59 | ); |
aoqi@0 | 60 | |
aoqi@0 | 61 | // filter use to filter out "j*" and concatenate rest with ":" |
aoqi@0 | 62 | // after uppercasing all strings |
aoqi@0 | 63 | print( |
aoqi@0 | 64 | reduce.call( |
aoqi@0 | 65 | map.call( |
aoqi@0 | 66 | filter.call(list, function(x) !x.startsWith("j")), |
aoqi@0 | 67 | function(x) x.toUpperCase()), |
aoqi@0 | 68 | function(x, y) x + ":" + y) |
aoqi@0 | 69 | ); |
aoqi@0 | 70 | |
aoqi@0 | 71 | // another list example involving numbers |
aoqi@0 | 72 | list.clear(); |
aoqi@0 | 73 | // make random list of numbers |
aoqi@0 | 74 | for (var i = 0; i < 10; i++) |
aoqi@0 | 75 | list.add(Math.random()); |
aoqi@0 | 76 | |
aoqi@0 | 77 | var forEach = Array.prototype.forEach; |
aoqi@0 | 78 | // print numbers in the list |
aoqi@0 | 79 | forEach.call(list, function(x) print(x)); |
aoqi@0 | 80 | |
aoqi@0 | 81 | // print sum of squares of the random numbers |
aoqi@0 | 82 | print("Square sum:", |
aoqi@0 | 83 | reduce.call( |
attila@962 | 84 | map.call(list, function(x) x*x), |
aoqi@0 | 85 | function(x, y) x + y) |
aoqi@0 | 86 | ); |