Set Interface
The Set interface is a part of the Java Collections Framework and is a subinterface of Collection. It represents a collection that does not allow duplicate elements. The Set interface does not provide any additional methods beyond those specified in the Collection interface, but it adds the stipulation that duplicates are not allowed.
Key Characteristics of Set
- No Duplicates: A
Setdoes not allow duplicate elements. Each element in aSetmust be unique. - Unordered Collection: The
Setinterface does not guarantee the order of elements. The insertion order is not preserved. - Single Null Element: A
Setcan contain at most onenullelement. - Implements Collection: The
Setinterface inherits all the methods from theCollectioninterface.
Common Implementations of Set
- HashSet: Stores elements in a hash table. It does not guarantee any order of elements.
- LinkedHashSet: Stores elements in a hash table with a linked list running through it, which maintains the insertion order.
- TreeSet: Stores elements in a red-black tree, which sorts the elements based on their natural order or a specified comparator.
Code Example
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import java.util.HashSet;import java.util.Set;public class SetExample { public static void main(String[] args) { // Create a HashSet Set<String> set = new HashSet<>(); // Add elements to the set set.add("Apple"); set.add("Banana"); set.add("Cherry"); set.add("Apple"); // Duplicate element // Print the set System.out.println("Set: " + set); // Check if the set contains an element System.out.println("Contains 'Apple': " + set.contains("Apple")); // Remove an element set.remove("Banana"); System.out.println("After removing 'Banana': " + set); // Iterate over the set System.out.println("Iterating over set:"); for (String item : set) { System.out.println(item); } // Size of the set System.out.println("Size of set: " + set.size()); // Clear the set set.clear(); System.out.println("Is set empty after clear: " + set.isEmpty()); }}Output
Set: [Apple, Cherry, Banana]
Contains 'Apple': true
After removing 'Banana': [Apple, Cherry]
Iterating over set:
Apple
Cherry
Size of set: 2
Is set empty after clear: true
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