How to iterate a HashMap in Java
There are several ways to iterate a HashMap in Java. However, the three listed below are the most common.
Three ways to iterate a Hashmap
- Using a for loop to iterate through a HashMap
- Using a forEach to iterate through a HashMap
- Using an iterator to iterate through a HashMap
1. Using a for loop to iterate through a HashMap
In the code below, hash_map.entrySet() is used to return a set view of the mapped elements. Now, getValue() and getKey() functions, key-value pairs can be iterated.
// importing library.import java.util.HashMap;import java.util.Map;// class for iterating HashMap.public class Iterate {public static void main(String[] arguments) {// creating HashMap.Map<Integer, String> hash_map = new HashMap<Integer, String>();// inserting sets.hash_map.put(1, "Thor");hash_map.put(2, "Iron man");// iterating using for loop.for (Map.Entry<Integer, String> set : hash_map.entrySet()) {System.out.println(set.getKey() + " = " + set.getValue());}}}
2. Using a forEach to iterate through a HashMap
In the code below, the forEach function is used to iterate the key-value pairs.
// importing libraries.import java.util.HashMap;import java.util.Map;// class for iterating HashMap.public class Iterate{public static void main(String[] arguments) {// creating hash_map.Map<Integer, String> hash_map = new HashMap<Integer, String>();// inserting sets in the hash_map.hash_map.put(1, "Thor");hash_map.put(2, "Iron man");// iterating it using forEach.hash_map.forEach((key,value) -> System.out.println(key + " = " + value));}}
3. Using an iterator to iterate through a HashMap
In the code below, an iterator is used to iterate the each mapped pair.
// importing java libraries.import java.util.HashMap;import java.util.Iterator;import java.util.Map;import java.util.Map.Entry;// class for iterating HashMaps.public class Iterate {public static void main(String[] arguments) {// creating hash_map.Map<Integer, String> hash_map = new HashMap<Integer, String>();// inserting value.hash_map.put(1, "Thor");hash_map.put(2, "Iron man");// setting up iterator.Iterator<Entry<Integer, String>> it = hash_map.entrySet().iterator();// iterating every set of entry in the HashMap.while (it.hasNext()) {Map.Entry<Integer, String> set = (Map.Entry<Integer, String>) it.next();System.out.println(set.getKey() + " = " + set.getValue());}}}
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