How do I efficiently iterate over each entry in a Java Map?

There are several ways to iterate over the entries in a Map in Java. Here are some options:

  1. For-each loop: You can use a for-each loop to iterate over the entrySet of the Map. This is the most concise option:
Map<String, Integer> map = new HashMap<>();
// add some entries to the map

for (Map.Entry<String, Integer> entry : map.entrySet()) {
  String key = entry.getKey();
  Integer value = entry.getValue();
  // do something with the key and value
}
  1. Iteration over the keySet: You can iterate over the keySet of the Map and use the get method to get the corresponding value for each key:
Map<String, Integer> map = new HashMap<>();
// add some entries to the map

for (String key : map.keySet()) {
  Integer value = map.get(key);
  // do something with the key and value
}
  1. Using an Iterator: You can use an Iterator to iterate over the entrySet of the Map. This is a more traditional approach that allows you to remove entries from the Map as you iterate over it:
Map<String, Integer> map = new HashMap<>();
// add some entries to the map

Iterator<Map.Entry<String, Integer>> iterator = map.entrySet().iterator();
while (iterator.hasNext()) {
  Map.Entry<String, Integer> entry = iterator.next();
  String key = entry.getKey();
  Integer value = entry.getValue();
  // do something with the key and value
  // use iterator.remove() to remove the current entry from the map
}
  1. Using a forEach method: If you are using Java 8 or later, you can use the forEach method of the Map interface to iterate over the entries in the Map. This method takes a BiConsumer as an argument, which is a functional interface that represents an operation that takes two arguments and returns no result. You can use a lambda expression to specify the action to be performed on each entry:
Map<String, Integer> map = new HashMap<>();
// add some entries to the map

map.forEach((key, value) -> {
  // do something with the key and value
});