Java AbstractMap hashCode() Method (original) (raw)

Last Updated : 20 Jan, 2025

The **hashCode() method of the AbstractMap class in Java is used to calculate a hash code value for a map. This hash code is based on the key-value mapping contained in the map. It ensures consistency such that two maps with the same entries have the same hash code.

**Example 1: Hash Code of a Non-Empty Map

Java `

// Java program demonstrate the working of hashCode() import java.util.AbstractMap; import java.util.HashMap; import java.util.Map;

public class Geeks { public static void main(String[] args) { // Create a HashMap Map<String, Integer> hm = new HashMap<>();

    // Add key-value pairs
    hm.put("Java", 1);
    hm.put("Programnming", 2);
    hm.put("Language", 3);

    // Get hashCode
    System.out.println("Map: " + hm);
    System.out.println("HashCode: " + hm.hashCode());
}

}

`

Output

Map: {Programnming=2, Java=1, Language=3} HashCode: -95421541

**Explanation: In the above example, it creates a HashMap and adds three key-value pairs to it. The hashCode() method calculates a unique integer value based on the keys and values in the map.

Syntax of AbstractMap hashCode() Method

public int hashCode()

**Return Type: It returns an integer representing the hash code value of the map.

**Example 2: Hash Code of an Empty Map

Java `

// Java programm to demonstrates the // hash code of an empty HashMap import java.util.AbstractMap; import java.util.HashMap; import java.util.Map;

public class Geeks { public static void main(String[] args) {

    // creating an empty HashMap
    Map<String, Integer> hm1 = new HashMap<>();
    System.out.println("Empty Map: " + hm1);
    System.out.println("HashCode of Empty Map: "
                       + hm1.hashCode());
}

}

`

Output

Empty Map: {} HashCode of Empty Map: 0

**Explanation: The above program creates an empty HashMap without any key-value pairs. The hashCode() method returns 0 because no entries exist in the map.