How to store predicates in configuration file in java -

How to store predicates in configuration file in java -

i have list of hashmap<string, real>. want access each element on list, apply predicate on , add together element list if predicate returns true.

for illustration suppose have list of hashmap - {(a, 15), (b, 17), (c, 12)}, {(a, 12), (b, 13), (d, 90)}. predicate a > 7 & b < 15 . apply predicate on each element of list , find sec element satisfy predicate. applying predicate should easy have access element , compare value values supplied predicate.

the part stuck how save such predicate in configuration file, such can converted class , new predicates can added without fiddling core code.

one way utilize nashorn javascript engine. write java script validation function each predicate, , store in java script file.

function pred1(a,b) { if(a>7 && b<15) homecoming true; else homecoming false; }

create , load predicate file. need mention predicate file paths in configuration file, , lookup paths configuration file.

properties property = new properties(); property.load(configuration file path goes here);

sample configuration file property:

predicatefilelist:test1.js,...

get property,

string[] filepaths = ((string)property.get("predicatefilelist")).split(",");

initialize , utilize script engine.

scriptenginemanager mill = new scriptenginemanager(); scriptengine engine = factory.getenginebyname("nashorn"); // utilize filepaths here instead of file name. scriptobjectmirror s = (scriptobjectmirror)engine.eval("load(\"test1.js" + "\");");

for each map in list, phone call predicate function passing arguments predicate function:

list.foreach(map->{ system.out.println(s.call(map.get("a"), m.get("b"))); });

java