Iterating through/Updating HashMap [duplicate]

Question

I know there are several ways to iterate through a hashmap, but what is a good way to modify a hashmap as you go along (other than just creating a new hashmap and getting rid of the old one)

I want something like

for (Map.Entry<String, Integer> entry : wordcounts.entrySet()) {
    String key = entry.getKey();
    Integer value = entry.getValue();
    if(blacklist.contains(key))
        //remove key/value for that key from wordcounts
    if(mappings.contains(key))
     //change key in wordcounts from one string to another based on the key's value in a <string,string> map (mappings)
}

Will it be possibly for me to modify my map while I'm going through it? Do i have to use an iterator?

Answer 1

Take advantage of the map: go through your other collections first and do your operations.

for(String blacklisted : blacklist) {
    wordcounts.remove(blacklisted);
}
for(String mapping : mappings) {
    String oldKey =    // get old key
    String value = wordcounts.get(oldKey);
    wordcounts.remove(oldKey);
    wordcounts.put(mapping, value);
}

Answer 2

Use Map.Entry.setValue to change the value of the mapping. If you want to remove the mapping, use setValue(null) use an Iterator.