Question

I have a

TreeMap resMap new TreeMap<String, Map<String, String>>(); 

I would like to filter and keep only entries that values contains a known pair, let’s say (‘mike’ => ‘jordan’), and avoid a loop like below

Is there in my included libraries apache.commons and google.common a filter method (that probably would do a loop too, but at least it’s less verbose

for (Entry<String, TreeMap<String, String>> el : resMap.entrySet()){
    if (el.getValue().get("mike").equals("jordan")){
        //
    }
}

Answer 1

You can use filters from Guava and the Predicate interface.

Predicate<T> yourFilter = new Predicate<T>() {
    public boolean apply(T o) {
        // your filter
    }
};

So, simple example would be:

Predicate<Integer> evenFilter = new Predicate<Integer>() {
    public boolean apply(Integer i) {
        return (i % 2 == 0);
    }
};

Map<Integer, Integer> map = new HashMap<Integer, Integer>();

Map<Integer, Integer> evenMap = Maps.filterValues(map, evenFilter);