Java Collection size() method

The size() method of Java Collection Interface returns the total count of the elements contained in this collection.

Syntax

Parameters

Return Value

The size() method returns the total count of the elements present in this collection.

Example 1

import java.util.Collection;
import java.util.HashSet;
public interface JavaCollectionSizeExample1 {
    public static void main(String[] args) {
        Collection<Integer> collection = new HashSet<>();
        //add integer values in this collection
        collection.add(34);
        collection.add(12);
        collection.add(45);
        System.out.print("The elements in Collection : ");
        System.out.println(collection);
        //returns the size of the collection
        System.out.println("Size of the collection "+collection.size());
    }
}

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Output:

The elements in Collection : [34, 12, 45]
Size of the collection 3

Example 2

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.concurrent.ConcurrentLinkedQueue;
public class JavaCollectionSizeExample2 {
    public static void main(String[] args) {
        Collection<Character> collection = new ConcurrentLinkedQueue<Character>();
        char i;
        for(i='a';i<='z';++i){
            collection.add(i);
        }
        //returns the total size of the collection
        System.out.println("Total alphabets : "+collection.size());
        System.out.println("collection : "+collection);
        List<Character> list = new ArrayList<Character>();
        list.add('a');
        list.add('e');
        list.add('i');
        list.add('o');
        list.add('u');
        collection.retainAll(list);
        // returns the size of the collection
        System.out.println("Number of vowels : "+collection.size());
        System.out.println("Vowels : "+collection);
      }
}

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Output:

Total alphabets : 26
collection : [a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z]
Number of vowels : 5
Vowels : [a, e, i, o, u]

Example 3

import java.util.Collection;
import java.util.concurrent.ConcurrentLinkedQueue;
public class JavaCollectionSizeExample3 {
    public static void main(String[] args) {
        Collection<Integer> collection = new ConcurrentLinkedQueue<Integer>();
        //returns true if the queue is empty
        if(collection.size()==0){
            System.out.println("The queue is empty.");
        }
        else{
            System.out.println("Total elements are : "+collection.size());
        }
    }
}

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Output: