Differences Between Collection and Collections in Java

In Java, Collection and Collections are important components of the Collections Framework. The Collection has various sub-interfaces such as Set, List, and Queue.

The Collections provides static methods to perform various operations on collections, such as sorting, searching, and synchronization.

Let's learn them one by one with proper definitions, syntax, and a suitable example.

The Collection Interface

In Java, the Collection is an interface, which is considered the root interface in the collection hierarchy. It represents a group of objects, which are known as its elements.

Some collections allow duplicate values and specific orders, whereas some do not allow duplicates and do not maintain any order. Here are a few important methods of this interface:

• add()
• remove()
• size()
• clear()

Syntax

Following is the syntax of the Collection interface:

Interface Collection<E>

Where the E is the type of elements in this collection.

Example

In the following example, we create a collection named languages using the ArrayList class and perform various operations such as size(), remove(), etc, to get the size and remove collection elements:

import java.util.*;

public class CollectionTest {
   public static void main(String[] args) {
      // Creating a Collection using ArrayList
      Collection<String> langauages = new ArrayList<>();
      
      // adding elements to it
      langauages.add("Java");
      langauages.add("Python");
      langauages.add("C++");
      
      // Displaying elements
      System.out.println("The collection elements are: " + langauages);
	  
	  //displaying size
	  System.out.println("The collection size is: " + langauages.size());
	  
      // Removing an element
      langauages.remove("Python");
      
      System.out.println("Collection after removing element: ");
      // Iterating through elements
      for (String lang : langauages) {
         System.out.println(lang);
      }
   }
}

The above program produces the following output:

The collection elements are: [Java, Python, C++]
The collection size is: 3
Collection after removing element:
Java
C++

The Collections Class

In Java, the Collections is a utility class of the Object class. The Collections class provides various static methods (i.e., call directly using the class name) that operate on or return collections.

Here are a few important static methods of this utility class:

• sort()
• min()
• max()
• fill()
• copy()
• reverse()

Syntax

Following is the syntax of the Collections utility class in Java:

public class Collections extends Object

Example

In the following example, we use the Collections class's static methods add(), sort(), min(), and max() to add, sort, and find min and max values in an ArrayList class:

import java.util.*;
public class CollectionTest {
   public static void main(String args[]) {
      //creating ArrayList
      ArrayList<Integer> list = new ArrayList<>();
      
      // Adding elements to the ArrayList
      list.add(5);
      list.add(35);
      list.add(20);
      list.add(65);
      list.add(50);
      
      //iterating over ArrayList
      System.out.println("ArrayList elements are: ");
      for(Integer i : list){
         System.out.print(i + " ");
      }
      
      //sort the ArrayList
      Collections.sort(list);
      
      //arraylist after sorting
      System.out.println("\nArrayList after sorting: ");
      for(Integer i : list){
         System.out.print(i + " ");
      }
      
      //retrieve minimum value using Collections class
      System.out.println("\nMinimum value: " + Collections.min(list));
      
      //retrieve maximum value using collections class
      System.out.println("Maximum value: " + Collections.max(list));
   }
}

Below is the output of the above program:

ArrayList elements are: 
5 35 20 65 50 
ArrayList after sorting: 
5 20 35 50 65 
Minimum value: 5
Maximum value: 65

Difference between Collection and Collections in Java

Below is a list of a few differences between Collection and Collections: