Set and Map in Java

In Java, both Set and Map are interfaces that are part of the Java Collections Framework.

A Set is an unordered collection of unique elements, meaning that it cannot contain duplicate elements. Some common implementations of the Set interface include HashSet, LinkedHashSet, and TreeSet. Here’s an example of how to create a HashSet:

Tweet

Set<String> mySet = new HashSet<String>();

A Map, on the other hand, is a collection of key-value pairs, where each key is associated with a corresponding value. The keys must be unique, but the values can be duplicated. Some common implementations of the Map interface include HashMap, LinkedHashMap, and TreeMap. Here’s an example of how to create a HashMap:

Map<String, Integer> myMap = new HashMap<String, Integer>();

Here’s an example of how to add elements to a Set and a Map:

Set<String> mySet = new HashSet<String>();
mySet.add("apple");
mySet.add("banana");
mySet.add("orange");

Map<String, Integer> myMap = new HashMap<String, Integer>();
myMap.put("apple", 1);
myMap.put("banana", 2);
myMap.put("orange", 3);

To access the elements in a Set or a Map, you can use methods like contains or get:

Tweet

if (mySet.contains("apple")) {
    System.out.println("The set contains an apple");
}

int value = myMap.get("banana");
System.out.println("The value associated with 'banana' is " + value);

Note that there are many more methods available for Set and Map that allow you to manipulate and query the collections in various ways.