This is example of algorithm of merge two lists of maps

mergeListOfDicts

public void mergeLists () {

    def first = [
        ["name":"foo","val":"1"],
        ["name":"bar","val":"2"]
    ]
    def second = [
        ["name":"foo","val":"666"]
    ]
    
    def mergedMap = []

    first.each { e ->
        second.each { e2 ->
            if(e.name == e2.name) {
                mergedMap.add(["name":e.name, "val":e2.val])
            } else {
                mergedMap.add(["name":e.name, "val":e.val])
            }
        }
    }
    
    println mergedMap
}

mergeLists()