Java HashMap Size Example

This example shows how to get the HashMap size using the size method of the HashMap class. It is sometimes also referred to as HashMap length or number of key-value mappings stored in the HashMap.

How to get the HashMap size in Java?

The size method of the HashMap class returns the number of entries or key-value mappings stored in the HashMap.

1	public int size()

This method returns the number of mappings stored in the map object. The return type of the size method is an int type.

import java.util.HashMap;

public class HashMapSizeExample {

public static void main(String[] args) {

//create new HashMap

HashMap<String, String> hMapColors = new HashMap<String, String>();

//get the size using the size method

System.out.println("Size is: " + hMapColors.size());

//add some key-value mappings

hMapColors.put("1", "Red");

hMapColors.put("2", "Green");

hMapColors.put("3", "Blue");

System.out.println("HashMap contains " + hMapColors.size() + " mappings");

}

Output

1 2	Size is: 0 HashMap contains 3 mappings

How to check if HashMap is empty using the size method?

You can compare the return value of the size method with 0 to check if the HashMap is empty as given below.

import java.util.HashMap;

public class HashMapSizeExample {

public static void main(String[] args) {

//create new HashMap

HashMap<String, String> hMapColors = new HashMap<String, String>();

System.out.println("is empty? " + (hMapColors.size() == 0) );

//add some key-value mappings

hMapColors.put("1", "Red");

hMapColors.put("2", "Green");

System.out.println("is empty? " + (hMapColors.size() == 0) );

}

Output

1 2	is empty? true is empty? false

This example is a part of the Java HashMap tutorial.

Please let me know your views in the comments section below.

How to get the HashMap size in Java?

How to check if HashMap is empty using the size method?

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