How can you iterate over all keys and values in a Map object?

In Java, there are several ways to iterate over all keys and values in a Map object:

1. Using a for-each loop over entrySet():

Map<String, Integer> map = ...;
for (Map.Entry<String, Integer> entry : map.entrySet()) {
    String key = entry.getKey();
    Integer value = entry.getValue();
    // process key and value
}

2. Using keys and getting values by key (less efficient):

for (String key : map.keySet()) {
    Integer value = map.get(key);
    // process
}

3. Using Java 8 and lambda expressions:

map.forEach((key, value) -> {
    // process
});

The first and third methods are preferable as they are more efficient and convenient.