difference between equals() method and equality operator (==) in Java? Example

In object-oriented programming, we often encounter situations where we need to compare the values of objects rather than simple data types. While the equality operator (==) is commonly used for value comparison, it may not work as expected when dealing with objects that can contain multiple types of data.

When working with objects, we rely on the `.equals()` method to accurately compare their values. Unlike the equality operator, which compares object references, the `.equals()` method is specifically designed to compare the contents or values of objects. It allows us to determine if two objects are logically equal, even if they are separate instances.

Therefore, when dealing with object-oriented programming, it is important to use the `.equals()` method instead of relying solely on the equality operator (==). By doing so, we ensure that the comparison accurately evaluates the values contained within the objects, leading to more reliable and precise comparisons.

The difference between the `.equals()` method and the equality operator (`==`) in Java can be summarized as follows:

Purpose: The equals() method is used to compare the contents or values of objects to check if they are logically equal. The equality operator (==) is used to compare the references of objects to determine if they refer to the same memory location.

Comparison Target: The equals() method is typically used to compare objects of a class to another object, usually of the same class. The equality operator (==) is used to compare any two objects, regardless of their types.

Overriding: The equals() method can be overridden by a class to provide a customized comparison logic. By default, it compares object references. The equality operator (==) cannot be overridden and always performs reference comparison.

Comparison Result: The equals() method returns a boolean value (true if the objects are considered equal, false otherwise). The equality operator (==) returns a boolean value (true if the object references are the same, false otherwise).

Usage: The equals() method is commonly used when comparing objects for equality, especially for user-defined classes. The equality operator (==) is often used for basic data types and comparing object references.

Here are some examples to illustrate the differences:

java
String str1 = "Hello";
String str2 = "Hello";
String str3 = new String("Hello");

// Using equals() method
System.out.println(str1.equals(str2)); // true (content comparison)
System.out.println(str1.equals(str3)); // true (content comparison)

// Using equality operator
System.out.println(str1 == str2); // true (reference comparison)
System.out.println(str1 == str3); // false (reference comparison)

Integer num1 = 10;
Integer num2 = 10;
Integer num3 = new Integer(10);

// Using equals() method
System.out.println(num1.equals(num2)); // true (content comparison)
System.out.println(num1.equals(num3)); // true (content comparison)

// Using equality operator
System.out.println(num1 == num2); // true (reference comparison)
System.out.println(num1 == num3); // false (reference comparison)

In the above example, we have two sets of comparisons. The first set involves comparing String objects (str1, str2, and str3). With the equals() method, the content of the strings is compared, resulting in true for both comparisons. However, when using the equality operator (==), the reference comparison is performed, resulting in true only for the first comparison where the references are the same.

The second set of comparisons involves comparing Integer objects (num1, num2, and num3). Using the equals() method, the content (numeric value) is compared, resulting in true for both comparisons. When using the equality operator (==), the reference comparison is performed, resulting in true only for the first comparison where the references are the same.

These examples demonstrate the different behaviors of the equals() method and the equality operator(==)  in Java, emphasizing the importance of understanding their distinctions and choosing the appropriate approach for object comparison based on the desired outcome.