How to Check if Two Maps are Equal in Java - Step by Step Examples

How to Check if Two Maps are Equal in Java ?

Answer

To check if two maps are equal in Java, you can use the `equals` method, which compares the key-value pairs of both maps. This method provides a straightforward way to determine if two maps contain the same elements.

✐ Examples

1 Checking Equality of Two Maps Using equals Method

We can check if two maps are equal in Java by using the `equals` method, which compares their key-value pairs.

For example,

We start by importing the `java.util.HashMap` class, which provides the necessary functions and data structures for working with maps.
We declare and initialize two maps named map1 and map2 with some key-value pairs. In this example, the maps have string keys and integer values.
We use an if statement to compare map1 and map2 using the `equals` method.
We print the result to the console using the `System.out.println` function to indicate whether the maps are equal or not.

Java Program

import java.util.HashMap;

public class Main {
    public static void main(String[] args) {
        // Declare and initialize two maps
        HashMap<String, Integer> map1 = new HashMap<>();
        map1.put("one", 1);
        map1.put("two", 2);
        map1.put("three", 3);
        
        HashMap<String, Integer> map2 = new HashMap<>();
        map2.put("one", 1);
        map2.put("two", 2);
        map2.put("three", 3);

        // Check if the maps are equal
        if (map1.equals(map2)) {
            System.out.println("Maps are equal");
        } else {
            System.out.println("Maps are not equal");
        }
    }
}

Output

Maps are equal

2 Checking Equality of Two Maps with Different Sizes

We can also check if two maps with different sizes are equal in Java by comparing their sizes first and then using the `equals` method to compare their key-value pairs.

For example,

We start by importing the `java.util.HashMap` class, which provides the necessary functions and data structures for working with maps.
We declare and initialize two maps named map1 and map2 with some key-value pairs. In this example, the maps have string keys and integer values, and they have different sizes.
We use an if statement to compare the sizes of map1 and map2. If their sizes are not equal, we print a message indicating that the maps are not equal.
If their sizes are equal, we use the `equals` method to compare the key-value pairs of both maps.
We print the result to the console using the `System.out.println` function to indicate whether the maps are equal or not.

Java Program

import java.util.HashMap;

public class Main {
    public static void main(String[] args) {
        // Declare and initialize two maps
        HashMap<String, Integer> map1 = new HashMap<>();
        map1.put("one", 1);
        map1.put("two", 2);
        map1.put("three", 3);
        
        HashMap<String, Integer> map2 = new HashMap<>();
        map2.put("one", 1);
        map2.put("two", 2);

        // Check if the maps are equal
        if (map1.size() != map2.size()) {
            System.out.println("Maps are not equal");
        } else if (map1.equals(map2)) {
            System.out.println("Maps are equal");
        } else {
            System.out.println("Maps are not equal");
        }
    }
}

Output

Maps are not equal

3 Checking Equality of Two Maps Using a Helper Function

We can create a helper function to check if two maps are equal in Java, which provides a reusable way to compare maps.

For example,

We start by importing the `java.util.HashMap` class, which provides the necessary functions and data structures for working with maps.
We declare and initialize two maps named map1 and map2 with some key-value pairs. In this example, the maps have string keys and integer values.
We define a helper function named areMapsEqual that takes two maps as parameters and returns a boolean value indicating whether the maps are equal.
Inside the helper function, we compare the sizes of the maps. If their sizes are not equal, we return false.
If their sizes are equal, we use the `equals` method to compare the key-value pairs of both maps and return the result.
We call the helper function with map1 and map2 as arguments and print the result to the console using the `System.out.println` function to indicate whether the maps are equal or not.

Java Program

import java.util.HashMap;

public class Main {
    public static void main(String[] args) {
        // Declare and initialize two maps
        HashMap<String, Integer> map1 = new HashMap<>();
        map1.put("one", 1);
        map1.put("two", 2);
        map1.put("three", 3);
        
        HashMap<String, Integer> map2 = new HashMap<>();
        map2.put("one", 1);
        map2.put("two", 2);
        map2.put("three", 3);

        // Check if the maps are equal using the helper function
        if (areMapsEqual(map1, map2)) {
            System.out.println("Maps are equal");
        } else {
            System.out.println("Maps are not equal");
        }
    }

    // Helper function to check if two maps are equal
    public static boolean areMapsEqual(HashMap<String, Integer> map1, HashMap<String, Integer> map2) {
        if (map1.size() != map2.size()) {
            return false;
        }
        return map1.equals(map2);
    }
}

Output

Maps are equal

Summary

In this tutorial, we learned How to Check if Two Maps are Equal in Java language with well detailed examples.

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How to Check if Two Maps are Equal in Java - Step by Step Examples