Java HashSet Cheat sheet
Tags: beginners, tutorial, programming, java
Published: 2023-04-12 14:03:15


>  Demo — [https://youtu.be/2tLxcaopKR4](https://youtu.be/2tLxcaopKR4)

    public class SetDemo {
        public static void main(String[] args) {
            //Initializing a new HashSet
            HashSet<String> mySet = new HashSet<>();
    
            //Adding values to set
            mySet.add("One");
            mySet.add("Two");
            mySet.add("Two");
            mySet.add("Three");
    
            //Printing set
            System.out.println(mySet);
    
            //Adding values in Bulk
            //Add values from myList to mySet maintaing unique constraints
            ArrayList<String> myList = new ArrayList<>();
            myList.add("Four");
            myList.add("Five");
            myList.add("Three");
    
            mySet.addAll(myList);
            System.out.println(mySet);
    
            //Accessing values using for-each loop
            System.out.println("=====for-each========");
            for(String element : mySet) {
                System.out.println(element);
            }
    
            //Accessing values using iterator
            System.out.println("=====Iterator========");
            Iterator<String> it = mySet.iterator();
            while(it.hasNext()) {
                System.out.println(it.next());
            }
    
            //Accessing values using forEach
            System.out.println("Using forEach and Consumer========");
            mySet.forEach(System.out::println);
    
            //Clearing
            //mySet.clear();
    
            //Check size
            System.out.println(mySet.size() + ", " + mySet.isEmpty());
    
            //Contains check -- constant time performance
            System.out.println(mySet.contains("Two"));
    
            //Removing elements
            mySet.remove("Three");
            System.out.println(mySet);
    
            //Retain elements
            ArrayList<String> keepThese = new ArrayList<>();
            keepThese.add("Four");
            keepThese.add("Two");
    
            mySet.retainAll(keepThese);
            System.out.println(mySet);
    
            //Converting set to Array
            Object[] arr = mySet.toArray();
            String[] strArray = mySet.toArray(new String[0]);
    
            //Using Stream
            List<String> fromSet = mySet.stream().collect(Collectors.toList());
            System.out.println(fromSet);
    
            //----------------------------------------------------------------
            //----------------- LinkedHashSet --------------------------------
            //----------------------------------------------------------------
    
            //Initializing LinkedHashSet
            System.out.println("=========LinkedHashSet==========");
            LinkedHashSet<String> lSet = new LinkedHashSet<>();
    
            lSet.add("One");
            lSet.add("Two");
            lSet.add("Four");
            lSet.add("Three");
            lSet.add("Three");
    
            System.out.println(lSet);
    
            for (String element : lSet) {
                System.out.println(element);
            }
        }
    
    
    }