What\'s the Difference Between `==` and `Equals()`/`equals()` in Java and C#?

Understanding the Difference between Equals/equals and == Operator

In programming, understanding the nuances between operators like == and Equals/equals is crucial. This question highlights a key distinction between these operators, specifically in Java and C#.

Reference Equality vs. Value Equality

Reference Equality:

The == operator in both Java and C# is used for reference equality. This means it checks if two variables (a and b) are referencing the same object in memory. In simple terms, it determines if a and b are aliases of each other.

Value Equality:

The Equals/equals method, on the other hand, typically implements value equality. This means it checks if the values stored in the referenced objects are equal, even if the objects themselves are not the same.

Java's Implementation

In Java, == always checks for reference equality, while Equals(b) calls the overridden Equals method from Object, which by default also checks for reference equality.

C#'s Implementation

In C#, it's slightly more complex. If there's an overloaded operator that handles the == operation for the specified types, it will be called. However, in the absence of an overload, == behaves like Java, checking for reference equality.

Overriding Equals

In both languages, the a.Equals(b) or a.equals(b) method calls the Equals method declared by Object, unless an overload has been defined by the execution-time type of the referenced object. Overridden implementations may perform custom equality checks, such as comparing specific properties or fields.

Null Handling

It's important to note that if a is null, attempting to call a.Equals(b) or a.equals(b) will result in a NullReferenceException/NullPointerException.

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