Shuffling Elements of Unordered Collections in Java
Unordered Collections in java does not provide any order i.e. the elements cannot be accessed using specific indexing or ordering as we could in the case of ordered collections such as List. Sets and Maps are examples of unordered collections.
In java, we cannot shuffle unordered collections directly using Collections.shuffle() method as it expects a List as a parameter.
For shuffling the elements,
- We have to first store the elements of the unordered collection inside a List, and then we can shuffle it using Collections.shuffle() method.
1) Shuffling Elements of a Set
Java
// Java program to demonstrate the shuffling // of a set import java.util.*; public class GFG { public static void main(String[] args) { // Creating a Hashset Set<Integer> st = new HashSet<>(); // Inserting elements to the set st.add(91); st.add(0); st.add(55); st.add(10); st.add(9); // 9 won't be inserted to the Set as Hashset does // not take duplicate entries st.add(9); // Displaying the elements of the set System.out.print("The Set before shuffling: "); for (int i : st) System.out.print(i + " "); System.out.println(); // Creating a List and storing the values of the // Set inside it by passing the Set as a parameter // to the constructor List<Integer> list = new ArrayList<>(st); // Shuffling the elements of the list using using // Collections.shuffle() method Collections.shuffle(list); // Displaying the elements of the list System.out.print("The List (containing elements of the Set) after shuffling: "); for (int i : list) System.out.print(i + " "); } } |
Output
The Set before shuffling: 0 55 9 10 91 The List (containing elements of the Set) after shuffling: 55 0 91 10 9
2) Shuffling Elements of a Map
Java
// Java program to demonstrate the shuffling // of a map import java.util.*; public class GFG { public static void main(String[] args) { // Creating a HashMap Map<Integer, String> mp = new HashMap<Integer, String>(); // Inserting some values inside the HashMap mp.put(1, "Geeks"); mp.put(2, "for"); mp.put(3, "Geeks"); mp.put(4, "is"); mp.put(5, "love"); // Displaying the map System.out.println("The Map before shuffling: "); for (Map.Entry<Integer, String> entry :mp.entrySet()) System.out.println(entry.getKey() + " " + entry.getValue()); System.out.println(); // Creating a list and storing the elements of the // Map inside of it List<Map.Entry<Integer, String> > list = new ArrayList<>(mp.entrySet()); // Shuffling the list using shuffle() method Collections.shuffle(list); // Displaying the list System.out.println("The List (containing the elements of the Map)" + " After shuffing: "); for (Map.Entry<Integer, String> entry : list) System.out.println(entry.getKey() + " " + entry.getValue()); System.out.println(); } } |
Output
The Map before shuffling: 1 Geeks 2 for 3 Geeks 4 is 5 love The List (containing the elements of the Map) After shuffing: 2 for 5 love 4 is 3 Geeks 1 Geeks
.png)