How to get size of a collection in Java

Problem Description

How to get size of a collection?

Solution

Following example shows how to get the size of a collection by the use of collection.add() to add new data and collection.size() to get the size of the collection of Collections class.

import java.util.*;

public class CollectionTest {
   public static void main(String [] args) {   
      System.out.println( "Collection Example!\n" ); 
      int size;
      HashSet <String>collection = new HashSet <String>();
      String str1 = "Yellow", str2 = "White", str3 = "Green", str4 = "Blue";  
      Iterator iterator;
      collection.add(str1);    
      collection.add(str2);   
      collection.add(str3);   
      collection.add(str4);
      System.out.print("Collection data: ");  
      iterator = collection.iterator();     
      
      while (iterator.hasNext()){
         System.out.print(iterator.next() + " ");  
      }
      System.out.println();
      size = collection.size();
      
      if (collection.isEmpty()){
         System.out.println("Collection is empty");
      } else {
         System.out.println( "Collection size: " + size);
      }
      System.out.println();
   }
}

Result

The above code sample will produce the following result.

Collection Example!

Collection data: Blue White Green Yellow
Collection size: 4