4 methods of traversing keys in Java Map

1. keySet iterates through keys

Iterator<String> iter = map.keySet().iterator();
while (iter.hasNext()) {
    key = iter.next();
}

2. keySet uses for loop to traverse key

for (String key : map.keySet()) {
    //key
}

3. entrySet iterates through keys

Iterator<Entry<String, String>> iter = map.entrySet().iterator();
while (iter.hasNext()) {
    key = iter.next().getKey();
}

4. entrySet uses for loop to traverse key

for (Entry<String, String> entry: map.entrySet()) {
    key = entry.getKey();
}

It is recommended to use the second traversal method.