HashSet Example
In this section we are discussing HashSet with
example code that shows the methods to add, remove and iterate the values of
collection. A HashSet is a collection set that neither allows duplicate elements
nor order or position its elements.
Description of program:
In the
following code segment we are performing various operations on HashSet
collection.
We have explained the steps to add, remove, and test the
elements of the collection. Keys are used to put and get values.
We can also
execute this code on a
Vector by changing the HashSet declaration and
constructor to a Vector as it supports the collection interface.
To
insert an element in the HashSet collection add() method
is used.
The size() method helps you in
getting the size of the collection. If you want to delete any element, use the remove()
method which takes index as parameter. In order to remove
all data from the HashSet use clear()
method. When the HashSet is empty, our program checks for it and displays a
message "Collection is empty". If the collection is not empty
then program displays the size of HashSet.
Here is the code of program:
import java.util.*;
public class CollectionTest {
public static void main(String [] args) {
System.out.println( "Collection Example!\n" );
int size;
// Create a collection
HashSet <String>collection = new HashSet <String>();
String str1 = "Yellow", str2 = "White", str3 = "Green", str4 = "Blue";
Iterator iterator;
//Adding data in the collection
collection.add(str1);
collection.add(str2);
collection.add(str3);
collection.add(str4);
System.out.print("Collection data: ");
//Create a iterator
iterator = collection.iterator();
while (iterator.hasNext()){
System.out.print(iterator.next() + " ");
}
System.out.println();
// Get size of a collection
size = collection.size();
if (collection.isEmpty()){
System.out.println("Collection is empty");
}
else{
System.out.println( "Collection size: " + size);
}
System.out.println();
// Remove specific data
collection.remove(str2);
System.out.println("After removing [" + str2 + "]\n");
System.out.print("Now collection data: ");
iterator = collection.iterator();
while (iterator.hasNext()){
System.out.print(iterator.next() + " ");
}
System.out.println();
size = collection.size();
System.out.println("Collection size: " + size + "\n");
//Collection empty
collection.clear();
size = collection.size();
if (collection.isEmpty()){
System.out.println("Collection is empty");
}
else{
System.out.println( "Collection size: " + size);
}
}
}
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Download this example.
Output of this program:
C:\vinod\collection>javac CollectionTest.java
C:\vinod\collection>java CollectionTest
Collection Example!
Collection data: Blue White Green Yellow
Collection size: 4
After removing [White]
Now collection data: Blue Green Yellow
Collection size: 3
Collection is empty
C:\vinod\collection> |
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