For each loop on Java HashMap

Question

A basic chat program I wrote has several key words that generate special actions, images, messages, etc. I store all of the key words and special functions in a HashMap. Key wor

Answer 1

Well, you can write:

for(String currentKey : myHashMap.keySet()){

but this isn't really the best way to use a hash-map.

A better approach is to populate myHashMap with all-lowercase keys, and then write:

theFunction = myHashMap.get(user.getInput().toLowerCase());

to retrieve the function (or null if the user-input does not appear in the map).

Answer 2

Only in Java 8 & above

map.forEach((k,v)->System.out.println("Key: " + k + "Value: " + v));

Answer 3

If you need access to both key and value then this is the most efficient way

    for(Entry<String, String> e : m.entrySet()) {
        String key = e.getKey();
        String value = e.getValue();
    }

Answer 4

A better pattern here might be:

Value val = hashMap.get(user.getInput());
if (val != null) {
    doVal();
}
else {
    // handle normal, non-keyword/specfial function
}

which takes advantage of the fact that HashMap returns null if the key isn't contained in the Map.