Ways to read Key from Java HashMap

Table of Contents

1. Using keySet()
2. Using entrySet()
3. Using getKeys() (Java 10+)
4. Using Stream API
5. Using Iterator

1. Using keySet()

    HashMap<String, Integer> map = new HashMap<>();
    map.put("Java", 1995);
    map.put("Python", 1991);
    
    Set<String> keys = map.keySet();
    for (String key : keys) {
        System.out.println(key);
    }
    

2. Using entrySet()

    HashMap<String, Integer> map = new HashMap<>();
    map.put("JavaScript", 1995);
    map.put("C++", 1979);
    
    for (Map.Entry<String, Integer> entry : map.entrySet()) {
        System.out.println(entry.getKey());
    }
    

3. Using getKeys() (Java 10+)

    HashMap<String, Integer> map = new HashMap<>();
    map.put("Ruby", 1995);
    map.put("Go", 2009);
    
    Set<String> keys = map.keySet();
    keys.forEach(System.out::println);
    

4. Using Stream API

    HashMap<String, Integer> map = new HashMap<>();
    map.put("Python", 1991);
    map.put("Java", 1995);
    
    map.keySet().stream().forEach(System.out::println);
    

5. Using Iterator

    HashMap<String, Integer> map = new HashMap<>();
    map.put("C++", 1979);
    map.put("JavaScript", 1995);
    
    Iterator<String> iterator = map.keySet().iterator();
    while (iterator.hasNext()) {
        System.out.println(iterator.next());
    }