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Deeply explore the differences between ==
and Equals()
/equals()
in Java and C#
In programming, the equality operator is crucial in value comparison. A common question is the difference between the ==
operator and the Equals
or equals
method.
For reference types (objects) in Java and C#, the ==
operator checks whether two variables refer to the same object, that is, reference equality. Instead, Equals
or equals
calls a virtual method defined in the Object
class, which typically validates the identity but can be overridden by a specific type, thereby implementing a value equality check.
Java implementation
In Java, ==
always checks reference equality, which means it determines whether two references point to the same object. There are no user-defined operator overloading in Java, so the behavior remains the same.
Flexibility of C#
C# provides greater flexibility in comparison. ==
Reference equality is enforced by default. However, if an overload exists for a variable of a specific compile-time type (for example, a string), that overload will be implemented. This overload can define its own behavior, typically implementing value equality, where two different references can have the same value.
Equals
and equals
In Java and C#, a.Equals(b)
or a.equals(b)
calls a virtual Object
or Equals
method inherited from the equals
class. This method checks for identity by default. However, it can be overridden in specific types to enable custom value comparisons, depending on the runtime type of the object being referenced.
Handling null values
Note that attempting to use Equals
or equals
with a null reference will result in NullReferenceException
or NullPointerException
.
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