core/src/main/java/io/fabric8/maven/core/util/MapUtil.java
public static void putIfAbsent(Map<String, String> map, String name, String value) {
        if (!map.containsKey(name)) {
            map.put(name, value);
        }
    }
public static void putIfAbsent(Map<String, String> map, String name, String value) {
        if (!map.containsKey(name)) {
            map.put(name, value);
        }
    }
Adds the given key and value pair into the map if the map does not already contain a value for that key