Yesterday, Brian Goetz (Lambda architect) suggested that I produce an example of Lambda being used from Nashorn. Since, I've been heads down in Nashorn, I really haven't played with Lambda that much. After looking at some examples from Stuart Marks, I figured, what the hey, it doesn't look that hard. Details of the Lambda APIs are available at JDK 8 b92 API .
Many constructs are familiar to JavaScript developers. The main things to note;
- where you can use a Lambda you can use a JavaScript function
- JavaScript arrays need to be converted to Java collections
- JavaScript syntax requires the '.' end a phrase, not start one (forces continuation)
Other than that, the JavaScript source and Java source looks very much the same.
#!/usr/bin/env jjs -scripting var copyright = <<<EOS; /* * Copyright (c) 2010, 2013, 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, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ EOS var Collectors = java.util.stream.Collectors; // Break the copyright into tokens. var tokens = copyright.split(/\s+/); // Convert to ArrayList. var list = new java.util.ArrayList(); tokens.map(function(e) list.add(e)); // The JavaScript collection for the result. var result = []; // Parallelize some of the activity. list.parallelStream(). // Select only words. filter(function(t) t.match(/^[A-Za-z]+$/)). // Make case comparable. map(function(t) t.toLowerCase()). // Fold duplicates. collect(Collectors.groupingBy(function(t) t)). // Move results to JavaScript collection. forEach(function(t) result.push(t)); // Sort the result. result.sort(); print(result);
The result;
a,above,advised,all,and,any,are,arising,be,binary,business,but,by,caused,code, conditions,consequential,contributors,copyright,damages,derived,disclaimer, documentation,endorse,even,event,express,fitness,following,for,form,from, goods,holders,however,if,implied,in,is,its,liable,limited,list,loss,materials, may,merchantability,must,name,names,negligence,neither,no,nor,not,of,on,or, oracle,other,out,owner,particular,permitted,possibility,prior,procurement, products,promote,provided,purpose,redistribution,redistributions,reproduce, retain,rights,shall,software,source,specific,strict,substitute,such,that, the,theory,this,to,tort,use,used,warranties,way,whether,with,without,written