List<Map> maps1 =[{"bigtypes":100,"num":400},{"bigtypes":200,"num":300},{"bigtypes":400,"num":500},{"bigtypes":600,"num":500}]
List<Map> maps2 =[{"bigtypes":400,"num":720},{"bigtypes":500,"num":320},{"bigtypes":200,"num":120}]
List<Map> maps3 =[{"bigtypes":700,"num":120},{"bigtypes":500,"num":320},{"bigtypes":100,"num":510}]
目的:bigtype属性値が等しいnum属性値を加算し、bigtype属性値が等しくないList