Difference Between equals() Method and == Operator in Java

Can you tell the difference between equals() method and equality operator (==) in Java?

Yes, in Java, the equals() method and the equality operator (==) serve different purposes and are used in different contexts when comparing objects.

== Operator

• The == operator is used to compare the references of two objects. It checks whether both references point to the same object in memory.
• For primitive data types (like int, char, etc.), == compares the actual values.

Example:

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

System.out.println(str1 == str2); // false, because str1 and str2 refer to different objects

equals() Method

• The equals() method is intended to compare the actual content or state of two objects. By default, it behaves like ==, comparing references, but it can be overridden in a class to provide a meaningful comparison based on the object's attributes.
• Many classes in the Java standard library (like String, Integer, etc.) override the equals() method to provide value-based equality.

Example:

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

System.out.println(str1.equals(str2)); // true, because str1 and str2 have the same content

Summary

• Use == when you want to check if two references point to the same object.
• Use equals() when you want to check if two objects are logically equivalent (i.e., have the same content).

Important Note

When overriding the equals() method, it is also a good practice to override the hashCode() method to maintain the general contract for the hashCode() method, which states that equal objects must have the same hash code.