How to Print HashSet Elements in Java?
In HashSet, duplicates are not allowed. If we are trying to insert duplicates then we won’t get any compile-time or runtime error and the add() method simply returns false.
We can use 2 ways to print HashSet elements:
- Using the iterator() method to traverse the set elements and printing it.
- Directly printing it using a reference variable.
Method 1: By using Cursor which is Iterator.
- If we want to get objects one by one from the collection then we should go for the cursor.
- We can apply the Iterator concept for any Collection Object and hence it is a Universal Cursor.
- By using Iterator we can perform both read and remove operations.
- We can create an Iterator object by using the iterator method of Collection Interface.
public Iterator iterator(); // Iterator method of Collection Interface.
- Creating an iterator object
Iterator itr = c.iterator(); // where c is any Collection Object like ArrayList,HashSet etc.
Example:
Java
// Java program to print the elements // of HashSet using iterator cursor import java.util.*; class GFG { public static void main(String[] args) { HashSet<Integer> hs = new HashSet<Integer>(); hs.add( 5 ); hs.add( 2 ); hs.add( 3 ); hs.add( 6 ); hs.add( null ); // print HashSet elements one by one. // Insertion order in not preserved and it is based // on hash code of objects. // creates Iterator oblect. Iterator itr = hs.iterator(); // check element is present or not. if not loop will // break. while (itr.hasNext()) { System.out.println(itr.next()); } } } |
Output
null 2 3 5 6
Method 2: We can directly print HashSet elements by using the HashSet object reference variable. It will print the complete HashSet object.
Note: If we do not know the hash code, so you can’t decide the order of insertion.
Example:
Java
// Java program to directly print the // elements of HashSet import java.util.*; class GFG { public static void main(String[] args) { // create HashSet object HashSet<String> hs = new HashSet<String>(); // add element in HashSet object hs.add( "B" ); hs.add( "C" ); hs.add( "D" ); hs.add( "A" ); hs.add( "Z" ); hs.add( "null" ); hs.add( "10" ); // print HashSet // we don't know hash code, // so we don't know order // of insertion System.out.println(hs); } } |
Output
[A, B, C, D, null, Z, 10]
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